My 1 year and 6 mnth old Hermans Tortoise

My Tortoise has stopped eating.

I give him a veried diet, cabbage, carrot, hay with dried meadow flowers in it and as a treat apple and kiwi.
He lives in a very nice veveriam which we heat to a constant temperature.
He comes out every day to have a wander.
He is a really lovely boy.
I have tried other foods but he dosen't seem intrested.
We weigh him every week and hast'nt put any weight on for at least 2weeks.
Should I be concerned he is drinking and eating sometimes but not as much as he was 2 weeks ago.