Russian not moving back legs

(Gracie)

I have a Russian Turtle that I have had for over 7 years. He has always been spunky and full of energy until this past month. He hibernated for about 2 months and came out of it fine (so I thought).

He shows little energy now and does not use his back legs at all. They drag around behind him. His front legs show plenty of muscle and he is able to pull himself along with them. His color looks good, eyes open and shut normally and I am not finding as much scat in his pen.

He has not been eating well and recently I have not seen him eat at all.

I feel like he needs a mate and a new home as we have him in a huge long aquarium. Feeding him all the right things is not always possible but he gets apples, lettuce, banana bits occasionally and some outdoor grass and dandelions when I pick it.

What do you think his problem is?

Appreciate all you can offer,
Gracie