Looks pretty wet to me. Is there a shower in the tub that gets used? However it happens I see a gut demo in the not too distant future for you and that bathroom.

Thank you for the heads-up about this future project you are right there is tub about a half a foot near by shown on the photo marked with red...

Yeah, no real saving that. Ultimately, it needs to be pulled and replaced. Sorry.....

I appreciate knowing that -I am wondering if there should be any sort of vapor barrier or anything between the dirt floor and these wood boards I'd always thought there was some sort of material this is a Florida home does anyone know if this kind of home should be left open like this so the house can breathe or is there another approach needed? When I say this kind of home I mean a 1953 cinder block ranch...

Is that a toilet across from the tub? Might the leak be from under the toilet?

I am not sure if there is a leak from the toilet, we do not hear it running, and I called plumber #1 today who said "check the meter, if it's not running there is no leak." So I am trying to get a second or third opinion - one that might be more "hands on" :-) (no leak visible or water above the tile).

The toilet can also leak from under it (broken wax ring or other) and the water would go out under the tile, not necessarily show on top of the tile.

Ah! Got it, thank you - I will read more about this.... will learn moremore

Could be from under the toilet - we had a small hole in the old lead flange that connected to the drain. We were doing demo anyway and took the toilet area down to joists

I am not sure if there is a leak from the toilet, we do not hear it running, and I called plumber #1 today who said "check the meter, if it's not running there is no leak."

The plumber gave you generally good advice but doesn't always apply. A toilet is a reservoir so, if the flange or wax ring have failed or if the flange bolts are broken or loose, the 'leak' would be an event confined to only when the toilet is flushed/ when the water is released from the reservoir, so to speak. So the meter wouldn't give you an indication of that.

try flushing the toilet - see if you see the water - my guess is lead pipe

Hello, This is a quick update - a second plumber (from a national chain) came by with a handheld scanner and showed the spots of moisture on the floor (confirmed it was not a simple stain). They said they could pressurize the pipes to force any pinhole leaks, but advised us against it as not likely to help. So that honesty was helpful. Our next step over the next few weeks is to have several crawlspace companies come in to check from below and provide estimates on work related to the joists. I will check back in if I learn anything meaningful (like a solution! or at least helpful next steps.)