yellow leaves edges early vegetation

I think this might be nitrogen deficiency, to be honest... And I know what you're going to think - "But I've treated all the other plants the same and this is the only one that looks like this!" ... Been there, done that! In fact, I have 3 plants growing now (my Glueberries) where one is a lovely green, robust plant and another is kind of scrawny and the third vehemently stays lime green (although she's finally starting to come around). I've treated them all exactly the same ... but my Lime Green Lady germinated that color so it's got to be something in the genetics. There will be difference in plants - they're kind of like humans in that regard. There's no need to remove her from the grow room - it's not catching! She might just need a touch more nitrogen than the others and so DO treat her a little bit differently... she's terribly young but you might want to try giving her just a HINT of some grow nutes... like 1/16 to 1/8 tsp per gallon - but understand you may have to flush her if she reacts badly to that! Also, know that nothing will improve the color of these particular leaves... you will only be able to tell if you've been successful in your approach by seeing what new leaves come in looking like. The only other thing I'll say here is that these aren't even true fan leaves yet... you're still early in the game. If this were MY grow, I'd wait to see what the fan leaves look like and then perhaps feed her SLIGHTLY heavier than you would normally when it's time for them all to get some nutes. Good luck with the grow... your other two grows looked great and I'm sure this one will as well!