I use the papertowel in a plastic bag method and then tuck it away above one of my leds for a few days and they usually have no problem. but ymmv.
The one that is small may even be a toof decay, i know those grow small and seemingly slow. also, don't transplant your seedlings. that's not good to do with autos. They need to be in their final pot from the beginning of life, if you transplant it you're going to shock it and it doesn't have enough veg time to recover.