Flooring Tile - bathroom floor issue

i wasnt sure exactly where to post this, but here's my question. (i am standing in my basement), as i look up at my wood-planked sub-floor that is under my upstairs bathroom, i see that the wood has become a dark color with tinges of white in it. it is still very solid though. if i had to guess, i would say that water is getting underneath the tiled floor when excess water gets on the floor. it may go down through my baseboard pipe hole. the grout is all in tact as well as the cauling around the toilet and tub. do u think this wood discoloration is a problem such as mold or something?

Mold, yes. If it is solid, let's catch it before it goes any further. Get a good mildewcide and spray the area to kill the mold and mildew. Next, pull your commode and change the wax seal. It looks like it could be leaking somewhat. I don't think you would get enough moisture from mopping the tile floor to cause the underlayment to turn black and mildew. Since you say you have tile, you may want to check the downset of the commode ring. If it sits below the level of the tile, obtain an extension ring and install it over the existing ring. They are usually the thickness of installed tile, so it will bring it up to proper height. Then install the new ring and toilet. Keep an eye on the area from beneath and keep it sprayed with the mildewcide from time to time to make sure it goes away.

i have changed the toilet seal several months ago and sealed the bottom of the toilet with grout. i have lived in the house for 1 1/2 years and this problem was here before that. im sure the house inspector would of noticed it. all the wood seems dry and the dark colored areas are in small different areas, not one big spot. what kind of mildewcide would u suggest anyway?

There are commercially available mildewcides at hardware stores and big boxes, but they all smell like sodium hypochlorite, so you may want to make a weak mixture of it and spray it on the area to see if it will alleviate the problem. Sodium Hypochlorite is bleach. Wear gloves and eye protection and don't let it drip on treasured surfaces you don't want white.
Sealing the bottom of the toilet with grout or silicone, really harbors the problem of a leaking toilet seal, as it will not allow the water to leak out and be noticed. It will stay inside the perimeter, and it only has one way to go, and that is to the wood below.

i wasnt sure exactly where to post this, but here's my question. (i am standing in my basement), as i look up at my wood-planked sub-floor that is under my upstairs bathroom, i see that the wood has become a dark color with tinges of white in it. it is still very solid though. if i had to guess, i would say that water is getting underneath the tiled floor when excess water gets on the floor. it may go down through my baseboard pipe hole. the grout is all in tact as well as the cauling around the toilet and tub. do u think this wood discoloration is a problem such as mold or something?

Our pipe was leaking from the bathroom above our basement and it had a lot of white stuff dripping down. The plumber said that this was 'soap'. Sounds like you have a nasty leak also. Check the shower pan?