Most likely mineral content is the issue. I’ve never gotten them myself, but I’ve seen photos where people got them after a couple of weeks. The commonality was that they didn’t dry the razor & blade. I also read a metallurgist say that putting a blade away wet will cause it to lose its sharpness quicker.I've read that before, but I've never had an issue with tea stains on my stainless steel razors (or any other razors), and I do not remove or dry the blade between shaves. I'm guessing that the mineral content of the water is a factor in this.