Post #1 says "by the tire." Is it on the inner sidewall?

I understand you think it's not brake fluid. If it's on the lower inner sidewall it's gear oil (stinky) or brake fluid. If not, it's something else.

My '11 lost a caliper like this and I've never seen such a clearly delineated failure: day one, fine. Day two, noticeable puddle under tire. Just parked overnight in my shop the caliper seemingly had a massive cardiac event and died.