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.
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.
Happy gardening in Hawaii. Gardens are where people grow.