I had same problem few months after my first stoma was done, 19 years ago. Suddenly bags not sticking properly, leaking and skin getting very irritated. Ended up going to see stoma nurse and changed bag types, seemed I had suddenly become allergic to the one I was using. So would suggest chat with ostomy nurse and try a different appliance if necessary.
Crohn's dx 1989, loop ileo 1992, end ileo 1992. Arthritis developed 1990 Stoma abcess 1995. Azathioprine started 1995. Panprocolorectomy 1999. Stillbirth 2000, antiphospholipid syndrome dx 2000. Flare up 2004, stoma abcess and strictoplasty 2004. Low blood pressure dx with impaired kidney function 2006, fludrocortisone pres. flare up 2010, steroids, Humira, codeine.