I am so sorry to hear that!
It can be an awful feeling to do all you can think of to do, and have to make that decision when one fails to thrive and you can't stand to watch it wither away.
Some animals just don't make the transition to living in captivity very well. Green anoles were the very first pets that I used to have. I had one that lived to be 5 years old. I had some that bred and laid eggs like crazy but they liked to dig them up and eat them. Each one is such an individual.
What were you feeding them? You might try feeding them canned cat food on a toothpick or in a bowl no more than twice a week. They will get all the moisture they need, calcium, and nutrients from it. If you do it more than twice a week, you risk kidney and liver damage. Entice them at first with it on a toothpick by their mouth...moving...so they recognize it as food. You might have to smear it in their mouth at first or
very gently force it open and put some in by squeezing the sides of the mouth gently, but usually if you put some in between the lip and the teeth, they taste it and eat it normally. Then, you might want to keep putting them by their food dish with some in it.
Good luck...and if your little one is gone, then I'm sorry about that, but maybe this is information you can use for another time.
