Having an accurite or anything to properly read the humidity will help you know if your humidity is high enough.
If you're worried about your tort not having enough humidity then you can make a humid hide.
But usually once the top layer dries out well though then it's time to add some more...
Also you want to make sure that your coir is not soaking wet.
I get worried about shell rot, so I have a nice basking rock (paving stones from Home Depot) that are under the lamp so they're always nice and dry.
Your goal is to have a dry top layer of coir while the rest is damp underneath...
I would definitely get rid of the aspen. For the same reason as the hay. Plus your tort has no need to ever eat aspen in its life.
They don't really need a more comfortable substrate in their hides. Especially since aspen is so dry it will do more harm than good.
I agree and would not use a sand/soil mixture easy. Way too many impacts toon horror stories for me.
Try using coco coir instead. It's bug free, clean (for dirt anyway), and retains moisture well.
And I would get rid of the heat mat as well and just strive for perfect ambient temperatures via...
I would get rid of the hay entirely to be honest. It definitely will mold and your tort doesn't need to eat it anyway.
I would avoid that other substrate you mentioned. But personally I'm wary of any substrate that promotes a tortoise eating it. I would just stick with the coco coir for now and...
While your tort isn't that big, you can try doing what I do as using the bathtub.
For me it keeps the water warmer longer. Plus the tub isn't really used for baths but for showers and I clean it after bath time anyway so it doesn't bother me. I do understand that it might bother some people...
Again, a 4'x4' won't last you very long for a sulcata but it is better than the 38 gallon.
You'll have to make sure you can keep the humidity high in it, otherwise your tort will get pyramiding.
Pics of the flower bed would help. But you need to have something enclosed to get the humidity levels up. Which either means you enclose the flower bed or you build your own enclosure.
What are the dimensions of the bed?
If you still haven't figured out the cause then I would definitely find a vet.
Even if the vet is a little far, it might be worth going to the one Zero mentioned. A good vet that's far away is better than a bad vet that's close.
I've only heard they make good pets from people trying to sell them as pets. That being said, I haven't heard that they make bad pets either. But I don't know many people that have them.
Don't let me deter you though! :D
I would just make sure you keep the tort and the prairie dog separate.
They're vaguely similar. Prairie dogs are slightly smaller I believe but I'm not sure that they would make very good pets.
I see them being sold in stores pretty often but I wonder how they would do once they reached sexual maturity (a good amount of "wild" animals made pets--raccoons...