Adding baking soda to the salt rinse may help, even with Glutamine powder, to help with healing. If the rinse burns, cut out the salt. It can also be a viral infection, like HSV, causing blisters, which may need antiviral medications, or appropriate meds for any other type of infection(s), which can be caused by treatment, a compromised immune system, or brought out of latency by such, so see your doctor for evaluation and proper diagnosis.
Good luck.