Huh? How does that work?

So. This week my drains were running slow, and I found myself standing in about 1/2" of water at the end of my shower, so I decided to be proactive and run some drain cleaner through. All seemed fine, the drains were running through very nicely, until this morning. This morning I found myself standing in two inches of water that wasn't draining at all. All I could say was, "Huh." When I finished my shower I ran some more drain cleaner through. Hopefully tomorrows shower will be puddle free.