I got a Crocodile Gecko for my birthday a few months ago, and he ped in September for no reason. Help?

I got Dimitri on June 22nd and he died in September. I fed him the proper size crickets, misted his cage, cleaned it regularly; there wasn't an apparent reason for his ping. Anyone happen to know what went wrong? It'd really help if I knew whether or not it was my fault. Thanks.