You aren't a failure. You are doing everything possible for your gliders, you got Thor to the vet and you caught this, a failure wouldn't have done that.
Every once in a while there are things you can't control that pop up, this is a learning experience. I know how scary it can be to go through antibiotics as I just did two rounds with one of my gliders because we thought she may have been severely sick. It is exhausting and brutal and scary but i promise you it is worth it. You are doing everything you can for your gliders and that is what matters most.