Do they bleed during flossing though? I used to get bleeding gums after brushing teeth, but switching to a softer toothbrush stopped it. Flossing, at the start, does cause my gums to bleed though.
My dental hygienist knows when I have been flossing and when I haven't.
If they start bleeding again it's a sign I've not been doing a good job staying on top of keeping them healthy.
After that, I never bleed during flossing. And I make sure to get it up between the gum and each tooth, so there’s a decent (but appropriate) amount of floss/gum friction.