What's Wrong?

I have 5 plants all growing in veg right now, i recently moved them from under some t8s into my new vegging chamber, a 400 watt HPS, temps in the box are always around 70-75 f. They are all growing in soil, 3 from seed, 2 from clone. Since ive moved them under the HPS the leaves on the plants have started to twist, and curl and become hard and brittle evetually dieing. When i look at the leaves there are no sign of visable insects, but the leaves look to be some what rusty. The plants are still growing, although not as fast as they should. I cant figure out whats wrong. Can anybody help with any insight, i apologize for no pics.

thanks
stanky