If you think there's any chance it's trans. related I would change the fluid just to be safe. Just once, I think the drain and fill x3 should really only apply to a neglected transmission or if you don't know how a used car was treated.

Are you getting gas from the same place as always (preferably a bigger chain so less chance of getting a "bad batch")?

Check or replace(it's due by now) the air filter and get back to us