I’ve had some success getting soured buttermilk smell/damp funky camper boy smell out of clothes with Woolite. Look for the version they make for washing machines now. It’s not too expensive, and a little goes a long way. Plus, it should be easy going on your yarns.
I’m thinking it’s going to take some enzymatic type stain remover/cleaner (and I think OxiClean is one of those) to break down the milk proteins to get the smell out.
I once spilled a cappuccino on the passenger side floor of my car…talk about a stiiiiiiiiinkyyyyyyyy smell for a long time, especially in the hot summer, icky! I don’t even recall what I did for it, I think just a lot of soaking and blotting, I didn’t have a steam vac at the time.
Here is a google search I did of “removing sour milk smell,” maybe that will give you some ideas. Do you have enough extra yarn to make a swatch you can test cleaners on to make sure they don’t harm your yarn?
I was thinking Woolite, and I thought I had some left, but I didn’t, so that was plan A for the Walmart trip. I’m hoping to finish the tank top tonight, then I should have some of the yarn left over to swatch to test the enzyme cleaners. I’m going to buy a couple different ones today and see what works.