Heres some pics

Your trees look good. I think the 90* is too hot and causes the soil to dry out too fast. The one white spot in the picture looks like a burn of some sort. Have you sprayed a chemical on it? Neem oil will cause burn marks. The white spots could be spider mites.

Pots that small would dry out to fast to have the fast drying soil. The pots are correctly sized for your trees to grow into. You've got "The Right Stuff". to propel into the future with nice trees

If you think the soil is not draining well enough, add more perlite or bark which is what I do. There are more options to supplement your soil to drain better, but I have no experience with them.

They need water.

It is very dry - you can see the soil detach from the pot sides because of soil shrinkage when dry. If you water now it will run off immediately giving you the false impression that it is fast draining. Peat become very hydrophobic (reluctant to re-wet again) once it is dry. Soak the pots in warm 80-85F water for 30 min to re-wet it. After that make sure to water again when the top 1 inch dries out for the smaller pots and for the taller pots wait till 2 inches is dry. With 600 HPS the heat will tend to dry the soil faster and the leaves will curl to conserve water.

I find they grow best at 74 to 84 degrees F.

They can also grow down to 69 but grow very very slowly and don't tend to do as well. Towards the upper end of that temperature range they often tend to dry out faster, so you have to keep a much more careful eye on them, more frequently watering to make sure the soil stays moist.

You might consider setting the HPS to a temperature thermostat outlet, so they only turn on when the temperature is below 82 degrees. That may help even out the temperature fluctuations.

If I were you I'd do that and then have a single 5000K LED bulb left on all the time.

Keep in mind that 600 Watts is creating a lot of heat, and that heat is not all being spread evenly throughout the enclosure, it's being radiated onto the plant, which could be causing the leaves to dry out, especially for plants in smaller containers, or if the light source is too close to the plants. When the plant's leaves are a warmer temperature than the surrounding air, you get a drying effect. The cooler air increases in temperature as it passes over the leaves, and as it does so it pulls out moisture. Also when air is warmed without moisture being added at the same time, that air will have a drying effect.

Actually, citrus can grow down to 55.4-F. Although the closer a tree gets to 55.4-F the slower the tree will grow. At 69-F a citrus tree will grow fairly well, 83-F is an excellent temperature for tree growth.

Thanks alot guys, i might have spilled some water or even nutrient enhanced waterwater (i use urine at a 1/10 waterwater ratio) might have used the feeding to though. I cant really change the temperature in the tent and im based in sweden so outside is a no no hehe. The weird thing is that when i ruffled the pot a little without watering, the droopy leaf corrected itself, i might add a little perlite as only 1 of the plantsplants has perlite in its mix, but ill make sure they are more wet im just really scared of rot root. Im also 100% certain theres no pests in my garden i inspect it very carefully each day.

Urine and manure is deadly to poncirus trifoliata and to some hybrids of pt. I am going to try urine one of 2 Seville sour oranges with the other being the control.

Steve

Steve is out control - lol.

Lemon Lime: What do you think cow manure is composed of? It will be hard to instruct cows not to urinate while doing their thing like us.

Urine is used in many countries as fertilizer. In Sweden (where OP is from) it is legal even for commercial purposes. Read this article from WHO written by swedish scientists: https://www.who.int/water_sanitation_health/wastewater/urineguidelines.pdf

It has been researched well and used in many countries.

There is nothing wrong with using urine from healthy person or cow for that matter as long as some basic safety guidelines are followed. By itself it is pretty sterile and high in Nitrogen, very low P and some K in it.

In container culture though, it has the same problem as adding compost/manure/urea to soil mix. You still need the nitrification bacteria to make N available to the plants. Most will be lost as ammonia. Or if the ammonia lingers too long it leads to ammonium toxicity.

Second problem with urine in containers is high salt content that depends on the person's salt intake. So it needs to be properly diluted and the soil should be flushed more often.

Thanks Bob

Steve

I apologize upfront for this post but I think I need to say this:

Allow me to me say a few words about my pet peeve. Lemon Lime just deleted his posts from this thread and for future readers my earlier comments will look like as if I am writing in vacuum. He has done this before in another [thread[(https://www.houzz.com/discussions/question-about-my-meyer-lemon-tree-dsvw-vd~5278427) when I engaged him in another debate. I find this approach particularly troublesome since it breaks the thread arbitrarily.

A forum like this is for exchange of information and at times one can be wrong/mistaken and I can be wrong too. I would happily admit my mistake, error or lack of knowledge if pointed out to me.

And to Lemon Lime: I encourage you to participate. I like you want to inject science into growing citrus. But if you are going write something then you should be prepared to either defend it or correct it. That is how science works.

Tropic, I agree. This makes question the veracity of Lemon Lime's statement.

If you both think it makes sense I can delete mine to. Otherwise I can leave it. I don;t remember what it said.

Thanks guys, i actually just prior to this post moved them into the tent where the 600w hps is placed, i might have spilled a drop of water that caused that sunburn (the whitewhite spot) as of right now they have aclimatized and are now back to normal growth, thethey were also topped at the same time which was probably not the best idea since it caused extra unessesary stress while they were getting used to the 600w hps. And yeah urine is great :)

On another note, would the citruses prefer my 600w hps or would my 40-60w LED be enough ?

Looks like the HPS is around 24 inches (70cm) away from the seedling plants and it should be OK there. To get an idea of light levels refer to this chart for a rough guide:

Water drops on plants should not cause sunburn. In nature it happens all the time and never causes any problems for leaves. It is a myth that water drops causes sunburn except in some rare cases. The water drop has to be a little distance away from leaves in order to focus the light into a small spots. So for hairy leaves it could happen and even then the burn will be a tiny spot.

The discoloration you see could be because of many reasons: chemical burn, build-up of excess salts, exposure to intense light, etc. My bet is on excess salts and combined with very dry soil is multiplying the effect. I would flush the soil well with water and leave it that.

Since it is an enclosed tent and temperatures are on the higher side, your plants will benefit from higher humidity and better air circulation. A small humidifier will achieve both at the same time. Or direct a small fan at a bowl of water inside the tent.

Ok thanks ill add a bucket with water again, a flush sounds like a good idea i saw some slight discoloration and color cracks in the older leaves aswell as some weird edges