Hey T'Mater-
I don't think your problem is with your
nutrients.
I think your
lights are way, way too high. Your plants have grown up in an effort to reach the light source. I will bet if you get those lights right down on top of the plants you will have a great deal more success.
However, I'm not sure you will have enough wattage there to really make those tomatoes grow, you may need to add some supplemental lighting, the more the better.
I too have used the General Hydroponics Flora series of nutrients and have had simply amazing growth on my Roma tomato plants. Mine are at the 90 day mark as well. Although the plants are only about 3 feet tall they are incredibly bushy and covered with blossoms, many of which are now bearing pea sized tomatoes.
Beautiful setup by the way. I am really impressed with how you did your system.
Good luck, keep up the good work!