Plant sprouted. second set of leafs brownish yellow. first sprout 1week in

Hey plant has been in for one week it sprouted looked great..now the second set of leafs are starting and they are dis colored. growing in Hydroponic grow cubes with nutes i checked water Ph its at 7
any idea whats going on? (this was bagseed)
thanks for reading take a hit maybe even hit me back with what you think
this is my first plant

Your water is fine, but those cubes are notorious for dropping the pH.. You gotta check the runoff

ouch alright I'll have to pickup Ph Up / down when i get paid