So still pretty young... You should also be feeding a lot more. Are we talking like a pinch of salt? Or a pinch of Copenhagen? That's a pretty good sized bio-load, and not knowing how much the auto-feeder feeds, I'm going to say it's not enough. I feed more than that and I only have 3 fish lol. Try and see what heavy feeding is going to do. You should start seeing your No3 raising after 3-4 days of that.
EDIT: You could also start dosing No3. Look into NeoNitro if raising your No3 "naturally" doesn't work.