Yes, it sounds like rot.
Owners replace floors in FG trailers all the time. But it is a major undertaking. I can't imagine paying someone to do it. Cost would be quite high. Ignore soft areas at your peril. Will only get worse. Need to find water source. When is the last time windows
were resealed? Doesn't sound like plumbing as you are getting leaks
when it is sitting. Refrigerator
vents are a second source. Roof vents, hood vent are also possibles. If floor is rotted up front, getting to the plywood under the bathroom is a big job.
Lots of threads out there on the web on rotten Casita
floor and repair. Casita
has changed their floor design multiple times since 1998. The trailer is designed like a bathtub. Any water that leaks
in cannot get out. So its like putting a piece of OSB in a bathtub filled with water.
Got to get the trailer under cover. Do you have room to put up one of those Harbor Freight carports? Drying it out but leaving it outside with its current leaks
is not going to work in GA. And you are going to need to get it under cover during the repair process. You are talking removing riveted cabinets, replacing floor in sections.
If your forecast is anything like ours this weekend (in the mtns) they are talking 3 inches of rain!
"over the past few years" + stored outside = serious.