Young dog with the beginnings of mouth problems.?

I have a seven-month-old spaniel/shepherd cross, and I've noticed that she seems to already have the beginnings of gum disease. A few of her teeth have a thin red line above them- the canines and some of the molars- and there is a tiny bit of rough yellow-white buildup in the creases of her back molars that I haven't been able to scrape off with my nails as before. She's fed dry food and chews on ropes, Nylabones and rawhides, and I intend to begin brushing her teeth every day. (I wasn't before, since I didn't want her to associate having her teeth brushed with pain from the places where she was still losing teeth). Is it normal for an otherwise healthy, active puppy this young to have the beginnings of mouth problems? Can anyone recommend what else I should be doing? Even brushing every day, will a dog eventually need to have a veterinarian scale their teeth regularly? How long, if left unattended (not that I intend to ignore this!) does it take for gum disease to set in?