HelpfulGardener.com

Any ideas about this leaf discoloration on the same hydroponic tomato from earlier in this post...it seems to be only on the lower leaves. The plant is still putting out new growth and flowers. I had one early tomato lost to blossom end rot but the cluster on the other mainstem seems to be doing fine. I started adding calmag so I don't think it's that...

it could be several things, hard to tell from the pictures. If it is only the bottom leaves remove them. Blossom end rot could be low calcium, but it could be too little water for that variety while the tomatoes are setting and expanding to size.

Blossom end rot usually is on the other end of the tomato, but there are a bunch of other things that can cause fruit rots. It could have be scalded and then rot set in. It could be a bacterial or fungal rot. Here it could even be rots from insects stinging the fruit.

I would think whatever is causing your fruit to rot is also affecting the leaves so bacterial or fungal disease. Look under the leaf and see if you see any pests on the leaf.

Nothing under the leaves. Have had recent issues with hornworms, slugs and yellow underwing caterpillars. All have improved with daily hand picking and bt spray.

The lower leaves are more affected than upper leaves...the lower leaves also have a little upwards curl but I was reading that is somewhat normal.

Often also the lower leaves on my tomato plants have discoloration, but it never was a problem. Instead some times it happened that some tomatoes have been affected by rot on opposite side of stem.

Do you use a staged nutrient solution? Tomatoes are high feeders so they can be tricky in hydoponics. PH out of range will cause nutrients not to be absorbed properly and tomatoes absorb nutrients at different rates at different stages of growth. Chlorosis on the lower leaves can mean there is a calcium deficiency. I don't know about the fruit rot, as I said blossom end rot usually is on the other end of the tomato.
https://ag.arizona.edu/hydroponictomatoes/nutritio.htm

We don't grow tomatoes in hydro, only in the aquaponic dutch buckets. We still get blossom end rot on some varieties, so we supplement with bone meal which the water does not have enough of. The pH of the water is about around 6.0.