tbh didnt notice any yellow, color is fine and should darken in the next 4-5 days, but the plant is a node or 2 less developed than mine were 8 days ago (well the ones i bothered to put in the bigger pots, the ones i had in 5oz solo cups looked like yours. I have 14 seedlings and only 11 pots lol. Oh.... Wanna buy 100 regular seeds of unknown but good genetics? about 65 of them came from plants with genetics from the 70s ? lol jk i dont like prison)
Anyways i suggest when you size up at the very least add a $5 bag of perlite to the mix and put the plant in a $0.50 walmart bag.