Thanks for posting! A brownish spot is normal, and with the warmer summer weather, can appear more frequently. It's a watermark, from water evaporating from the towel and your mother "breathing". If you scroll down on the main chatroom page, you'll find a heading titled "Ashley's DON'T-do LIST". This is a space where I address some common questions. Here's a link to #4, where I talk about cleaning and mention the watermark on the towel: http://www.maryjanesfarm.org/download/wild-bread/admonitions/admonition4.pdf