Yellow new growth

Ive got 9 chem dawg's sisters in a grow tent under a 600 watt hps. They are looking great and their doesnt seem to be any slow growth but the stange thing that is Happening is all the new growth all the leaves are pure. Yellow and then as they get bigger green starts filling in and then they look completly normal. Judt want to check that this isnt some weird problem. Room temp is 80's lights on 70's off. Good circulation with fresh air intake. Humidity is low at 20-40%. Growing in coco 3 gallon pots. H&g a/b nutes with rhizotonic and a light dose of calmag. Feeding every other day 1/2 gallon. Thanks guys for reading

Micro nute deficiency. Zinc? As has been said...we need pics, but the fact it's new growth rather than old leaves means it probably isn't the main mobile nutrients (NPK).

But bear in mind....New growth in dark indica varieties like Kush will always be lighter in colour than older growth, so it could just be that if you're a total noob?