When mine did that it was because of low platelets.

Are you flossing everyday? Brushing twice a day? It’s important to brush along the gum line with a soft toothbrush.

I thought that might be so when my blood work came back platelets were within normal. Maybe electric toothbrush and water pik too strong? I asked my oncologist if it can be from medication and he had no answer for me. Any other ideas from anyone who has experienced this?