Did you happen to check the cover over the raw water intake for the head? I checked mine after the yard had painted my bottom and found it had been painted over and that water flow was severely restricted. Did you have her painted before you took her home? If not did the surveyor make any notes about such things? I agree with SD you could also have a blockage. Any Zebra mussels where you are or she was when you bought her?
Just a thought....