Soggy subfloor and discolored linoleum near shower
I have a fiberglass bottom shower with marble sheets for walls and a glass sliding doors. I have noticed the linoleum is disclored and soggy underneath but only in the corners near the front of the shower were you step in. I have recaulked the whole shower with a good silicone and also in the metal frame corners that hold the doors. I am pretty sure water is not coming from inside the shower unless the fiberglass has a crack I can't see. There is no staining of the ceiling in the downstairs closet which is under the shower. Water must be moving laterally from drain area in the subfloor. I have a metal strainer that snaps off the drain and I see a piece that screws into the bottom part of the drain assembly that needs a special tool to unscrew. It looks like there is a gasket there and it looks compressed and old. Could this be the source?