That's not likely to be light burn. It doesn't look right to me. The compost is too 'hot' for seedlings, so they're getting a little fert burn. I've seen plants survive much worse as seedlings, but you do have to flush. Lucky for you, they're little and easy to deal with.

The advice about ditching the HPS for now is sound. You definitely want a little more in the blue end for seedlings. CFLs, tube flouros, or MH is appropriate. Too much red light too erly can make plants express as males at a higher rate.
stinkyattic Reviewed by stinkyattic on . Day 10 from seed/ Here's 2 pics of my plants, there's substantial yellowing on some of the leaves. They are growing in compost designed for tomatos. They are off a 400w HPS lamp, watered every 2/3 days depending on how dry the soil is, no nutes are being added to the water, they are on 18/6. I don't really want to flush the plants but if thats the best course of action I will do. Any ideas guys? Heres some images of the two worst affected plants so far. Cheers guys:thumbsup: Rating: 5