Dampness smell from tank?

[RenW]

Hey, I've been posting a fair amount on here recently but just got a lot of questions, sorry
I got a tank second hand and it has been cleaned out multiple times before I put anything in it. I decided to just go ahead with it and have filled it up and my hamster has been loving it. However, there is still the smell of dampness coming from the tank. I assume because it was used as a fish tank before. It was cleaned and dried thoroughly but the smell is still there and somehow worse with the bedding? Not awful but it's definitely there.
Has anyone dealt with this before? If so, were you able to solve the problem? Or is it just how its gonna be from now on?
Thank you