hey guys! im on my first grow, so i dont have a WHOLE lot of experience, but lets see if i can help...
if your usin miracle grow, it has time release nutes that most small plants just cant handle, cept for a few strains that are used to heavy nute uptake. doesnt look like nute burn to me, nute burn the tips will yellow first, then turn brown and the leaf will start to cup (which urs dont seem to be doing)...reason for this is theyre tryin 2 save all the condensation they can for the extra moister...so i would probably go ahead and eliminate that, also since u been givin em nuttin but water...
as for the exact problem, i coudlnt say for sure, but my plants have had leaves to yellow and die from time to time from sprout till up even now halfway thru flower...from wat ive read, this is pretty normal and common. so really, just keep an eye on her, let her do her thing and see if the problem continues...just remember, ur leaves already discolored wont go bac to normal, so just keep eyes on the new growth..good luck to both of u!