The walls seem to be dry, but the floor around the base of the toilet is reading 90% or higher moisture on a Klein Tools ET140 moisture meter. . . so I suspect that the wax seal is no longer sealing.
I've turned off the water, flushed the toilet to drain out as much of the water as I can, and set up a fan to pull the moisture out of the floor (there's an access panel on the opposite side of the wall).
I checked the walls and ceiling on the first floor under the location where the toilet sits and they are reading at 17% to 20%, which is what other walls in the house read. I also checked the wall behind the toilet and it's also at 17% to 20%. I have been careful to change the mode on the moisture meter to "masonry" and "drywall." Checked other toilets in the house and they are at 40%, which seems high as well.
I'm inclined to call a plumber to repair the toilet even though I've done other plumbing work before. Opinions?