When we were at the Goshen rally last year, we had the very same problem. Great pressure in everything but the bathroom sink. We had this addressed by the Heartland service team. Solved in 10 minutes. It was plastic shavings built up in the lines. I do not know how the solved it so quickly, but it now has great pressure. I think they might have used a back flow pressure to solve the issue. Not sure, maybe give Heartland a call and see if their service team can give you some advice.
Jamie