Hello T'Mater,
Deciding to stop using the "flora-Gro" was a mistake. Unlike in soil where mixing different brands, and/or lines of
nutrients and additives is common. Growing hydroponically dosen't have the same buffer of nutrients in the soil to make up for compensations, thus is not nearly s forgiving. Use 10mL (2 Tsp) per gallon of all three (Gro, Bloom, and Micro) for your
nutrient solution. Give your plants about 2 weeks to to show recovery. Keep the ratios basically even, but you can add a few mL more per gallon of flora bloom, and/or drop a few mL per gallon of gro if desired. But you need all 3 parts of the nutrient solution to work properly. Cutting any part out of the mix will result in deficiency.
Your lighting may be an issue too, but tomato's have been known to be successfully grown using florescence's with 'enough light," (keywords "enough light"). I need to look up the info again but I believe 6500K is on the high end of the blue spectrum (6700k the very top, and better for foliage), and the lower the "K" number, the more on the red end of the spectrum (better for flowering plants). But with enough light your plants should flower with either spectrum of florescent
lights.
P.S.
60 on/off may also be an issue. The Sure To Grow
growing medium holds moisture easily (just like rockwool), and may be limiting oxygen to the roots.
You can get the same amount of water time by using a 30 on/off cycle, or even better 15 on/off cycle time. But may only need 15 on, and 30 off cycles. Do you have any pictures of your setup? You may also be able to get more oxygen to the roots with better drainage (regardless of cycle times).