Looks like multiple nutrient deficiency - what are you feeding them with and how much each time?

Dave

I've been feeding them with a tomato fertilizer of 16-19-29 on Fridays for the past two weeks because they are all starting to flower. I go by the instructions and break about 2 gallons up between the tomato plant and the three cherry tomato plants, so about a half gallon each. I add a half tsp per gallon of water, per containered plant instructions on the fertilizer. I also gave them some epsom salt, 2 tbsps in two gallons of water a few days ago. When I initially planted them, I did put some Jobes Organic 4-4-4 in the dirt, not nearly enough for the size of the pot because I wanted to fertilize with the liquid mostly and know how much they are getting, so some of that is in there too. Or was. They've been outside for probably about 5 weeks now and have grown immensely. I'm not a tomato growing expert by any means and just trying to learn what is best so far, so any advice is appreciated. The new growth looks great though.

Should I be fertilizing them more often, you think? Is it a deficiency of one of the NPK's?

Please post an image of the entire plant.

If the new growth looks good and this is all mostly on old growth then I suspect it was simply from not feeding them soon enough. They were planted out 5-6 weeks ago but only fed 2 weeks ago. That nutrient poor stretch of time likely caused this problem. Plants need nutrient supplements from they time they develop their first set of true leaves and regularly thereafter. The only issue is how you supply those nutrients. When growing in containers nutrients leach out every time you water so need to be replaced regularly.

But that doesn't mean they need BIG doses all at one time either. 16-19-29 is a very high dose fertilizer that could easily be fed at half strength or even 1/4 strength, just more often to better maintain the levels in the soil. Plus does it also have micro-nutrients? NPK is not all the plants need in a container. You also have to supply the micros they would get from growing in dirt.

Method of applying is the other issue. Water the plants fully first and then feed the fertilizer mix. See if that works for you.

Dave

I noticed this same thing on a few lower leaves of my Big Beef tomato plant. The plant is very healthy otherwise.

I made my own medium this year, and added blood meal, bone meal, lime and compost. I wondered myself how long it would take the plant to use up the nutrients before supplemental feeding. I suppose there are too many factors to really figure that out. I've begun using fish emulsion feedings every 7-10 days.