worried about sprouts (1 week)

Its been a week since I started growing my plants. I started by germinating them in rockwool cubes and after 4 days I transfered them directly into my hydro system (view pic#1) where they have been for 4 days (light: 1- 18 hours, 2- 20 hours, 3- 22 hours) and 3 of them fell! They all have 2 sets of leaves (1 big pair and a new smaller pair, view pic#2).

Im keeping the closet door open to reduce the temperature (from 31 celcium ~88F) so the stems will be stronger, and I have a coord and paper loops going around the plants for support, to keep them upright.
I have been spraying them with weak germination solution (according to the hydro nutrient directions) as their roots arent long enough to reach the hydro pool yet, I spay them about 3 times a day.

Everything seems to be fine, the stems are whiteish green and the plants look healthy, I have been bending the stems lightly to build strength.

Does anyone have some suggestions? Should I worry about their weakness? The stems are kinda long, I think I put them in the hydro system too late (the stems were like 3 inches before I moved them).

BTW, the light im using is a 430w Son Agro HPS bulb. It has increased blue spectrum and the stems dont seem to be getting much longer since moving the plants under this bulb.
Thanks in advance for any suggestions/replies. Comments welcome.

EDIT: The bulb is about 4 feet over the plants, its in a closet, the door is usually closed but its well ventilated cause I open the door often and kind of fan the door so its circulates air in the closet. The medium in the hydro system is pH balanced (treated) rockwool. There is more than 3 gal. of hydro solution per plant in each rubbermaid bucket.