Need some emergency help

This is a first time attempt at areoponics. I have eight plants growing in a 16 pot system. They were all started from seed in rockwool cubes about 4 weeks ago and then placed in the net pots. They were progressing beautiful until this morning when I noiticed two were drooping. The stems appear to be weakening about an inch from the bottom. The bottom inch looks thinner and brittle almost likes it's drying out. The roots sre being sprayed every five or six minutes for one minute with the following nutrients; (these are all per one gallon of water) 3 tsp of B.C.Boost, 1 1/2 tsp of B.C. Grow, 1/2 tsp of Thrive Alive B-1 Red, 1/2 tsp of MagiCal and 2 tsp of SugarDaddy. PH adjusted to 5.8 to 6. The light is a 400 watt MH placed about 16 inches above the plants. Any help would be greatly appreciated.