You need to brush more often, sounds strange but the gums bleed through not doing the job properly, you don't necessarily brush harder, best to use a small soft brush at this age and go up and down not across, brush say 3 times daily and thoroughly and the bleeding should stop, good luck and look after those teeth, I estimate that to repair each adult tooth later, say with a cap you are looking at a thousand dollars a tooth not to mention how difficult life can be with a set of false teeth, not that I have them thank god, cheers mate from roccolina