I have an old female Ball Python nearing 20 years in age. She has really thinned out and become frail in this last year and a half and has started having trouble with her food.

Around Thanksgiving she got her usual 2 medium feeder rats and though she has always been a slow eater, she took unusually long with these two and ate one of them backwards.

When I went to feed her this evening she couldn't kill any of the rats. I got 3 small ones because the store was out of medium and when I put the first one in she struck it quickly, but didnt have a very good bite on it and for the life of her could not exert enough force to constrict the animal.

I let her go for about 30 minutes until i started moving her and trying to get her to release and get a better bite.After she let go, I took the rat that had been suffering for 30 minutes and fed it to my other python.
I tried a new rat with my old snake and she couldn't even get a good enough bite on the animal to keep it from moving. I took the rat out and knocked it out and tried to see if she would go for it then. But alas she did not.

She is extremely frail and feels ancient when you hold her. I'm worried she may not be able to feed herself any longer. Is this common behavior for a snake that is nearing the end of it's life? Thanks for any responses.