That looks troubling. If you haven't already, look into some claybar to clean that up gently.
The trunk area is pretty bad for holding water after a wash.
As for eco's paint, a good detailing is best. I never found automatic washes be to very good, and if it's applying a somme kinf of wax in the process, it's probably sealing in some dirt.
If you can get a couple of buckets with grit guards, some nice towels, using a lot of running water and a gentle hand will go a long way for your paint.