droopy wilting leaves...am i boned?

My uncle has a SH bubbleponics system and he is having some serious problems. At first one plant started having really saggy droopy leaves. It was the only plant to have bugs so i figured that it might be dying from that. However overnight a second plant displayed the same symptoms. There are no real color distortions. All their leaves are just drooping real low, not even trying to find the light. My uncle is in the 4th week of growing and he asked for my advice. I don't know what to tell him. Why are two of the plants doing this? How can I fix it if possible? Will the problem spread to other plants???