Without claiming to be an expert... and basing advice on the given information, I see two things:

#1- The FIRST two leaves (Cotelydons) will lose vigor, become pale, and usually is not something to be concerned with.

#2- (assuming your plant IS just growing its Cotelydons) You should not be fertilizing your seedling. At this young stage, it only requires water, air, and light. Any non-nutrient additives should only be used when a serious problem is evident after careful research, and the application must be precise.

Again, I do not claim to be an expert, but I think I have read every thread on this website...... twice! :thumbsup:

Stay and Keep :jointsmile:
(I wish we had a little "Happy Grower" smileyface with a watering can or something)