well, definitely incubate them and keep an eye on them. if they are fertile and you candle them again a few weeks you should start to see a dark area like a shadow in the egg where the gecko is forming.

she could have retained sperm but it is odd that she would wait until it is getting cooler to lay. usually if they aren't laying but retaining sperm they will lay after it starts warming up (for instance, if they have retained sperm over the winter months, they will lay in the spring).

one last thing to consider--you are positive that post-it is a female right? how much does post-it weigh and how old is she?