How to address son's 'teen' habbits?

My sons have fully hit their teen years, if you know what I mean. I told them they need to do their own laundry now but they rarely do it. The only way the place will be clean and stench free is if I do it for them. More than a few times (okay, just about EVERY time) I have come across their crusty sheets or bath towels. First off, I dont want them doing that to the bath towels. Their sisters use those towels too! Secondly, I am unsure why my one son in particular tends to spritz into his own bedsheets. He sleeps in that bed, after all. I dont get it. Well, the thing is, I left each of them a note on their bed for when they came home from school that said, "I've asked you politely to do your own laundry. Mom can't handle your mess any more. You are young adults and must clean your own mess." I taped it to a box of ziploc bags so they can use that instead. That was at least a week ago. I noticed in my one son's drawer is the bag, obviously used multiple times, while my other son go the right idea and just used each bag once. I am unsure how I should approach this mess a second time. I dont want my son to be any more embarrassed than he already is and I dont want him to know I handled his spritz. I ALSO dont want him to keep using the same bag time after time. It is obvious it will get disgusting very fast. The odor inside that bag alone was enough to turn me away from my husband for a day or two. How, pray tell, do I go about handling this again? Do I just write him another note? Do I ask his father or priest to step in? Do I just let it go?