If you are talking about the 2 round leafs that first showed when the seed popped they are called Cotyledon. Yes they turn yellow and fall off. 14 day's is fine by the time you get your second set of true leafs the plant has entered the Vegetation stage and you need to transplant it.

Peace
Zandor Reviewed by Zandor on . Leafs Are Yellow...? Hi, I moved the light closer (hps 250W) and overnight the first set of leaves (the roundish ones) have turned completely yellow, they don't look dead, infact they look a healthy yellow, but what do I know... The plants have grown hell of alot overnight, the cannabis shaped leaves look healthy, nice and green. Are the roundish leaves meant to turn yellow, cause I read that they do fall off, my plant is about 14-17 days old. Any ideas? Thanks Dude0 Rating: 5