Milksnake gone off his food

[Cydonija]

Hi guys. I have a 2 year old pueblan milksnake who has suddenly gone off his food.

He has always been great strike feeder, and on small to medium frozen mice. His viv is usually around 87F during the day and down to 70F at night, but he has a hot pad that is set to about 75F. He is otherwise healthy and active, happy to be handled and has good muscle strength.

About 8 weeks ago he showed no interest in food, no matter what or where I fed him. He has pooped once a week for the last 3 weeks, the last one being more urine than anything, with a bit of calcified (the white stuff) so now sure he isn't constipated or impacted.

Any tips or tricks would be gratefully recieved