Bathroom Condemned

We are down 1/2 a bathroom. The guest bath on the main floor has started emitting toxic fumes. I suppose they can't be classified as toxic as Al can't smell anything but I am going nuts. I can't really describe the smell, it isn't gross but it definitely doesn't belong in my house. I did a light cleaning yesterday morning, a super deep clean last night, and then tonight Al scrubbed his guts out. Still the smell lingers. We have no idea where the smell could be hiding. Or what our children could have possible done/put in there to create such havoc. Our only solution is to keep it locked up with the fan running and hope that it goes away.