Little piece in DADGAD

Having tuned my Fender acoustic to DADGAD I went looking online for chords, and I found a nice I IV V progression, with a Cmajor shape as a break. Not sure what chord C becomes but it plays C, E, G, Bb and D (bottom D muted)
An app  tells me its Gm6add11...

Fender DG5, D'addario EJ15s