Why is seedling curling and yellow tip!?

did u feed her with Ca,Mg ? then it's P,K block

Nodes look fairly close, maybe reduce light until some interndods develop - possibly amping back up after that if it was slightly stunted. the curling is probably environmental - heat or low RH - combination of the two resulting in a high vpd. more than one thing causes tip burn and maybe just a fugly early leaf, too... i'd see how it progresses in order to eliminate possibilities.

At that stage, most likely overwater.