Suffering Father

I've brought my father to 2 e.n.t. a dentist and oral surgeon, and uconn test and smell clinic. They found bacteria and a fungal infection. Both have been taken care of. The problem still remains that he has gunk in his mouth which he says is coming from the back roof of of his mouth. It's thick and sticky and stick to his tongue and teeth.  He also can't taste his food.
He is 87 and on meds. Cymbalta being one. Bp meds low dose. Meds for Prostate. The only change in meds he's had in the past year is the Cymbalta addition. My mother also passed. This problem is now been for a year,