I had the exact same problem in the same spot and it was tranny fluid leaking. I noticed it and didn't think it was my car. Then while driving on the highway my car started smoking from the bottom and through the back really bad so I pulled over and noticed that the exhaust had been drenched in this red fluid that the heated exhaust system was burning off.

I had the car towed in to the dealer and in 1 day they diagnosed and fixed the problem. It was a failed tranny seal.

Now car is ok.