I have lived in my home for a year and keep replacing the master shower caulk when it gets mold/mildew. This has happened twice and I cannot determine what is taking place. It appears the mold/mildew growth starts in about the same locations and is behind the caulk. Is this a sign that there is mold behind the tile and grout showing a more significant issue? I cannot easily check behind the shower in anyway. No signs of leaks in the drywall below. Or is this just a simple maintenance headache?
That usually happens when you apply caulking over some semi-clean surface, there could be soap residue or something that allows water seep underneath caulking layer and eventually promotes mildew growth. Of course there could be some other issues like caulking quality (I would recommend silicone instead), not mildew resistant caulking/silicone, no sufficient ventilation (even mildew resistant caulk will eventually get contaminated without proper ventilation), water seepage behind tiles / along the shower base, shower base rim, etc… hard to say without seeing the actual shower assembly.