Hard to tell if insulation is wet.
Generally, if a tank is 10 years and over, we like to replace them.
We go out to a home, and there's water. We fix the first source we find, and yet there is still water leaking. At his point the time spent is nearly what a replacement would have taken us. And we may be only getting months more use at best with the repair.
Many condo associations require homeowners to replace at ten years, it's much cheaper then paying the $1,000 deductibles on the repairs after the fact.
Or, you can pull the covers off, put a fan on it and see if it dries up. That would be easy.