Cresteds, from my experience with mine and what I've read here, seem to have pretty wildly variant food preferences - for a while mine ate nothing but crickets, now seems to be switching to cgd/fruit, and I've heard of some that eat nothing but cgd and/or fruit before, so it may be that. However, if it seems like he's not eating anything, you may be best off to get him checked by a vet - zero appetite in a little guy that should be feeding like crazy to fuel growth is probably not a good sign. If it were me, I'd rather get him checked out only to find out nothing's wrong than not check and have the little guy have a serious problem that could have been easily taken care of if it was caught earlier.
Another question, though, is related to the crickets - what size are they relative to his head? Pooh-Bear seemed to grow relatively slowly at first, and then once she was big enough to eat medium sized crickets, she just grew like crazy. Do you know what Wesley was being fed by the pet store/breeder you got him from? If it was fruit/baby food, you might try mixing cgd with some organic baby food to transition him over to that.
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0.1 Albino Leopard Gecko - Tigger
0.1 Crested Gecko - Pooh-Bear