Plant trouble

Ok folks

Well the problems started in the veg stage but are still apparent in the flowering stage

My plants were browning at the leaves and the lower plants were begining to curl and fall off. My smallest plant has started to develop these white spots on the leaves.

The temperature and humidity are fine. Could it be due to over watering?. At the moment they are on a 12/12 cycle with a 125 florescent flowering bulb and i water them every 2 days. Or could it be a sign that they are not getting enough neutrients?

Pics will be coming once i find my camera :P. Until then has anyone got any idea's?