The same thing happens to my Jayflight 263RBS when camping in cold weather. We are not full timers. Last trip, lows were in the high 20's and I got this.
I could not run my MaxxAir fan on the lowest setting all night because it kept the trailer too cold and made the furnace run constantly.
After we made dinner and took our showers (2 of us), I ran the MaxxAir fan on high for about 30 minutes or so. That helped and there was a lot less condensation the next morning. Of course, that makes it freezing cold in the bathroom.
Others have suggested leaving the bathroom vent open (not running) and cracking a window somewhere. I am sure that will help too.
Looks like the Jayflight models are pretty much fair weather campers. I wish I had upgraded to the Eagle with Extreme Weather package. Better insulation I would imagine and less condensation issues.
Hopefully others who have them will chime in.
Best campers for wintertime camping. Only 1 Jayco made the list.