There is a link between gut issues and mental health. If you address the IBS, the depression might go away. I met a guy who said he has Crohn's and major depression that ended his marriage. The depression went away when he started taking a high quality multivitamin and doing treatment for Crohn's. The drugs they give for it suppress the immune system though so will likely cause more problems in the long run...possibly making the tinnitus worse and adding more problems. So if it were me I would address it naturally by healing the gut with bone broth, colostrum and probiotics. There is a diet called the Gut and Psychology Syndrome (GAPS) diet. Look into it if you are so inclined.
Tinnitus can be caused by some drugs. For me it's usually dehydration so I just drink a lot of purified water when I have tinnitus but I have a very mild case. Hopefully yours is mild too. There are a lot of people on the forum dealing with horrible tinnitus so I'm sure someone will chime in with better advice.
