Yellow stains on shirt collars?

Since living in Japan a lot of my light colored shirts developed yellow stains. I never had this happen in my life before and I thought I was going crazy til I went to book off bazaar and saw plenty of shirts with the same yellow staining around the collars on both men's and women's clothing.

I reckon this has something to do with the fact basically all washer machines are cold rinse only or something. Anyone have the same issue that only started after coming to japan or did I just suddenly start oozing yellow oil? Any remedies?

by hyuunnyy