Very weak ball python

[weak ball python]

I have 3 ball pythons, 2 female and 1 male, and the male has become extremely weak and lethargic. The 3 snakes share a large terrarium with heat ~80f. this is the same setup ive used for as long as ive had them. 2 days ago was feeding time. both females ate their rats without issue, but the male was unable to kill his. he kept a bite on the rats head and kept it coiled for 3 hours, but never killed it. eventually i killed it for him. he started to eat it, but was unable to swallow more than the head and spit it out. yesterday i got him much smaller prey. he ate a mouse pinkie, although it took 2 hours and he never killed it. he then ate a mouse hopper, but it again took hours. i moved up to the rat fuzzy, but despite holding on to it for hours, never killed it. he now seems uninterested in the rat.

during the struggle with the original rat i believe the rats claws did some damage as there are now 2 spots half way down his body that have lost the green scales. the skin does not seem to be broken and he isnt reacting any differently to being touched near the spots.

i usually feed once a month and it is not unusual for him to refuse food for months at a time. he has gone as long as 9 months, but without ever losing strength or energy. this time, i believe its been 4 months but he has lost significant mass and has almost no strength. if i pink him up he mostly dangles limp although he will lift his head and occasionally flick his tongue. I am not sure what to do at this point. he does have food in his system now although a pinkie and hopper mouse arent much for a 3.5 foot snake. there is only one vet nearby that could tell me anything but i cant get there for atleast a few days.

he was a rescue so i do not know his age but the female that was rescued with him is perfectly healthy. i have had them for about 10 years and they were mostly grown when i got them.

i bought more pinkie mice today in hopes he would be interested in more slow food, but he expressed little interest.

any thoughts on what i should do would be greatly appreciated. i do have a few pictures but i cannot post attachments for some reason.

edit:
i just read about possible dehydration.

(quoted)
Dehydration can also cause appetite loss. If the neck skin had been abnormal, that is a sign of severe dehydration, which can only be treated by a vet. I am very concerned because you said your snake seems weak and limp. Buy an electrolyte solution. In the USA, that would be unflavored Pedialyte In the UK, it would be a product called Lectaid, which is sold in pet stores. In Australia, it’s a human product called Dioralyte. Prepare a shallow bath consisting of 1/2 water and 1/2 electrolyte solution. Soak your snake for about 20 to 30 minutes twice a day. Reptiles can absorb the electrolytes and fluids through their vents (where droppings pass out), so make the water deep enough to cover the vent. Be sure to supervise closely.
(end quote)

the skin under his neck looks like it is sunken into the neck ( in one of the pictures that i cent upload) so definitely not normal.

does this change how i should go about treating him?