I'm gonna guess that some of the grow details and info is off here bud. On a look, you appear to be growing in soil, not coco??? If it is, in fact, a soiless medium then some additional info and details on nutrients and EC/TDS would be helpful. That said, looks like just a little bit of pale colouring to your first set of leaves based on the photos. If this is indeed the very first set that grew out then it can be somewhat common for them to yellow off a little and die out as the rest of the plant's leaves outgrow them and prevent your grow light from penetrating through. Not really an issue to worry about IMO. If you're in soil then it's definitely not an issue and almost expected as far as I'm concerned. Hope it helps and if you've got any other details you think we should know, hit me back and we can chat on it. Cheers👍