Betta Fish: Is he going to make it? :(

I had to leave again for five days, left specific instructions for the sitter and measured food. 11 gal tank, I thought he was doing better and his bloat went down, I came back he seemed more swollen and now has the white mass under his mouth. I just moved him into an isolation tank because he’s so still that the shrimp are picking at him. What can I do at this stage? he’s about 1.5 yrs old.