Because maintaining oral hygiene is the most important during the correction process! Maybe you didn't maintain your oral hygiene well during the correction process. I suggest you go to your doctor in charge and do a current periodontal condition assessment to see whether you should continue the correction or combine periodontal maintenance now. This will have a negative impact on your correction. Helpful!

The flesh that you mentioned falling off where the gums connect to the teeth should not happen during the correction process.

It may be considered that the gums have receded, which is possible during the correction process! The best thing is to ask your doctor in charge, he will know your situation best!

Hope it helps!