yellowing leaves during veg?

So i have 4 clones about 1 month in veg,i put them under my 400w last week,my temps are 25-28c my humidity is 30% i have them in a batmix soil but within the last week i have noticed alot of yellowing,i have give them 3 small feeds in the last week its only getting worse,i dont think this is a nute problem though,as i checked my other cuttings the same age under my 200w cfl,there beautiful green!,its only the ones under the hps that are yellowing...? what could this be?

it can be nute lock out due to ph. check ph, maybe flush the soil