General Hydroponics Flora Series Nutrients (Grow,Micro,Bloom) Discussion

I need some advice on nutrient feeding in an ebb and flow hydroponic system. At what point is my plants strong enough to feed on the mild growth stage on the nutrient feeding schedule (include plant height,age,etc.). I am starting my plants on a 400 watt metal halide tomorrow, they are in 2-20 watt fluorotubes and they are almost 2 and a half weeks old from seed. 3 of them have excellent growth but one of them is still quite small. Please help out if you use and are familiar with General Hydroponic Flora Series Hydroponic Nutrients. Any help is appreciated - Thank You.

I use the same nutes in a DWC set up and start the mild growth part on 2nd to 3rd week from seed.
1st week plain ph 5.8 water, 2nd seedling nutes and 3rd mild growth.

I am new at the DWC and have a set up with a plastic tote and a irrigation spliter with six hoses feeding six plants. When the roots reach the water do I stop using nutrients, and use ph balanced water.

That's when you have the nutes ph balanced in your reservoir.