Pervasive Kahm Invasion

I have a really, really stubborn invasion of Kahm yeast and can't seem to do the right things to get rid of it. Somehow, my mother starter was infected and I had to dispose of it. It was a year old when I threw it out.

I made another starter and it immediately showed kahm on the surface on day 3. My starter jar only allows enough head space for double its volume in expansion, and it has a one way vented lid, so I've tried to really limit oxygen in the container.

I don't want to keep trying if there's something I'm doing causing repeat invasions. I'm not a fan of the scent or taste of it and want to stop this from happening.

• I use Star San no rinse sanitizer on all of my tubs and utensils, including my scale (surface wiping).
• My flour is stored in air-tight containers in a cupboard, but they're all opened while I bake or feed starters.
• My water source is from the tap, which I don't sanitize beforehand.
• I use raw honey from a commercial retailer for feeding and baking.
• I use pink rock salt for baking (not feeding) that I grind myself in a spice mill that is also heavily cleaned but not sanitized
• I vlean my countertops with kitchen cleaner, but I don't do an additional sanitizing step.

Any ideas? I'd like to figure it out so I can keep a new starter going.