Here is the home made container:
a 5 gallon bucket, a 4 litter water reservoir at the bottom.

Right now, when it's hot (35 degrees Celsius) I need to water twice a day because the water reservoir is empty by noon.

Here is the pot ready to receive the plant.
I used 20 litter of dirt, mixed with one cup (300gr) of dolomite and a strip (one cup) of 8-8-8 fertiliser.

I planted the plant as far away from fertiliser strip.
I covered the dirt with plastic sheet.

This is the plant now (2 months after transplant).
It 120cm high (4 feet)

Observe the main and secondary branches

This is the first fruit cluster.
Observe the brown spots. Other fruits (that appeared later) don't have this problem.

Since I can't upload more than one photo in a message this is a link with leaves that developed problems:

https://www.dropbox.com/sh/4yptvjwbgnqqhg0/AACQBkMaujx5IZmYY9JMhiwOa/disease?lst#/

I would hate to loose the plants after all this work. What can I do to save the plants?

I used 20 litter of dirt, mixed with one cup (300gr) of dolomite and a strip (one cup) of 8-8-8 fertiliser.
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First: What kind of "DIRT" di you use ?
If you did not use potting mix/soil then that maybe part of your problem.
I see the plant in the picture getting too much water and not getting nutrients.

Instead of adding regular granular, you should have added Slow Release type. Even then after a month or so you should have started supplementing by fertilizing with liquid fertilizer .

Lastly, I see a problem with the water sitting at the bottom all the time.

It is SWC. Water is supposed to sit on the bottom.

I love you bucket.

It lookls like a very nice though awefully small self-watering container.. But if that is a drain hole coming out of the bottom side of the perforated res top and going through the outer bucket, it seems too low to me. The perforations IMO in the reservoir insert probably won't serve much as they are very small. Try 1/4" holes next time. I think your wicking is happening mainly from the sides.

The other problem in high temperture is you have the container all black and covered with a rather black plastic. This will create a heat sink and cook your roots. I recommend immediately wrapping the bucket with aluminum foil and ther top opening for a little more aeration/evaporation action which in addition to helping the roots be oxygenate, will allow for heat transfer out of the box.

The yellowing on the fastest growning plant may be due to a weakened plant from the heat cooking issue adding to the nutrient unbalance. Pinch off all of the leaves which don't look like good producers for the plant and look like they are spreading disease. Those are the ones that are severely dried out or more discolored than not.

Also, that patio in this heat is not helping as brick is clean, sure, but also impermeable to water, that's why old style Roman ovens were lined with it.

The plant may have disease, but be battling it and holding it at bay. You need to ckeep it cooler with the above sort of tips and be sure it is well fertilized as already mentioned.

The first pic may left hand tomatop looks like it has sunscald. Try covering your ripening tomatoes with a piece of cardboard of Sun is directly striking them. I use pieces of card stock junk mail that are about 5"x8" and tear them once to the center and insert those over the stems of vulnerable tomatoes. The right hand green tomato with the rot or scarring at the blossom end may be, but if it isn't on all the tomatoes it can also be the result of initially having been against the stem or fruit. In any case unless the problem is general I wouldn't worry about it.

The hotter it is the more blossoms fall off. Heat is your set up PLUS the external temp and humidity. In the Florida heat, I had a time with 0% setting. but am now back to around 1/4 of them and I care for my plants 5 times a day like a mother hen.

It is SWC. Water is supposed to sit on the bottom.

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I know what it is called.
The fact remains that the plant is sitting in the water all the time.

20 liters of dirt

Should be ok, I missed that and just noriced; the bucket looked small in the first pic with nothing for scale. I would have drilled a plain and simple 1 cm drain hole in the outer bucket up about 2.5 cm higher, and optimally hoped for 10 inches of soil mix between it ant the soil surface, but you may have another type of design I don't appreciate. The water capacity as you have found is too small. Your tomato will transpire ("drink") about 2-3 liters per day under these conditions.

Thanks for answering !

Here are more details:

The dirt I used I bought it from gardening department store.

One bucket it's peat plus sand and some root growth hormones (this is the first plant that grew faster, but it's most yellow.
Other two buckets is just peat. This dirt is denser than the above mix.

The plant does not stay in water. The wicking takes place around the perimeter of the green pot.

A plant drinks 6-7 litters of water a day now (I have to fill the bucket twice a day).

Here are some pictures of diseased leaves

Brown spots. This leave is green though

I don't think your plant looks that bad. As you have discovered BER, or blossom end rot often appears on the first fruits and then disappears. Dolomite lime can take months to break down and become available to the plants. Reusing most of your potting mix helps but be sure and add more dolomite lime each year.

Granular fertilizer, which you used is what is recommended by Earthbox and what most use, not slow release. Tomatoes however are nutrition hogs and I do supplement with Calcium Nitrate weekly. Many use other liquid or water soluable ferts.

Its common to get yellowing lower leaves as the plants begin to set and ripen fruit as the plant uses the available nutrients to produce fruit. It does look like your plant could use some supplemental feeding.

Yellow leave and some holes in it.
I inspected the plants for worms, but could not find any.

Should I spray my plants with some solution ?

"A plant drinks 6-7 litters of water a day now"

No, there is no way that plant needs more than 3 liters per day. If you've measured properly (and it is not draining out, I interpret my comment about overheating the soil as being the *principal* problem. Fix that!

When the leaves get to that stage I pinch them off. I don't know whether the curl is from heat and dying alone, or if there is something else there, but it look not bad so far. The only reason to keep a leaf like that is if it is shading a fruit and keeping the sun off. Otherwise keeping it on the plant will only increase the chances a weakened plant will get an out of control disease, IMO, because they are are good media for breeding of pathogens. The plant has already withdrawn nutrients from it which as seysonn mentioned may not be optimally delivered. The damage doesn't look too bad (diseased) to me, could be prompted from insects and the plant naturally removing nutrients from it to give to nerw growth. Nothing wrong with pinching off leaves from the bottom as the plant gets taller and puts out more in the zones where the new fruits are developing.

While the above ground plant can tolerate those high temperatures,the roots are in overdrive and very uncomfortable. This will just weaken your plant.

I just saw your last two pictures. The dark spots look like some type of leaf disease. I live in a dry arid climate and don't have too much of a problem but most spray with a fungicide type product. Remove the spotted leaves.

The first post with the light green leaves and darker centers looks like it could be spider mites, or it could be nutritional. Shake a leaf over a white sheet of paper or paper plate and see if you see teeny tiny bugs. Spider mites are difficult and require a product that is labeled as a miticide. I use powdered sulfur.

Also, sand is not a good addition for self watering containers. I too have grown in straight sphagnum peat but it is better to mix in some perlite, and/or bark chips to help the roots get oxygen.

The green leaf with brown spots looks diseased to me, My comments were for the first pic.

I have some dolomite left . Should I add to the water ? Will it help ?

If not, what kind of fertiliser I should use? I understand more potassium, less nitrogen is good for fruits.

Really nutritional deficiencies are hard to predict and we don't know what is in your water (enough magnesium Mg?), but I would suggest you check your label for micronutrients in the fertilizer to be sure it contains at least iron and manganese (Mn). Potassium rate (elemental) should be double or triple nitrogen.

I would add some iron first and foremost, and if my water were soft a little epsom salt (Magnesium sulfate heptahydrate) from the pharmacy or grocery store.

Good luck.