Don't beat yourself up too badly. Cresteds are different from many other comony kept herps in one way...
If you go with cresties again (and I hope you do!) I have a suggestion. With crested geckos, cooler is usually better. They are tolerant of cool temperatures for short periods of time, but not warmer temps.
That's not normally the way most people think when it comes to their reptiles. Too cool = problems for the most part.
I am highly prized for my meat. :eb: