I have no idea whether this will apply to your model trailer. I'm not at all familiar with your model.
I'm 99% certain that some of my floor water damage in my 23b was because the wheel arches weren't properly sealed. My guess is that the outer trim pieces kept the water out for a time. Once the seal on those exterior plastic pretty pieces got bad the water was able to get via the poorly sealed wheel arches and then in under the vinyl floor covering.
If your damage extends out from the wheel arches, or even touches that area it may be worth inspecting the seal between the outer skin and the wheel arch assembly. That said, if there is wall damage extending down to the floor area damage then you may have roof leaks.
I did some fixin' (not full blown repairs) to get our rig user friendly. It has worked very well for us. The trailer has been great.
Not that you asked.
As a carpenter I'm certain that your standards are higher than mine. Just keep in mind that most everything you do will not raise the value of an old, repaired trailer. If you're doing it for yourself then it is all worthwhile, but you are unlikely to recover your cost with resale.
Some of my wheel arch information is here.
Have fun. vic