When in doubt, change the water out. Err, I mean water change.
I'm a bit of a newbie myself, but I read numerous threads about people doing all the right things and still having problems with nitrates etc. I came to the conclusion that both these people and myself didn't have the right bacteria in the water. I used seachem stability and I ended up with good water parameters about a month later. this is very anecdotal and not a controlled experiment because I was making other changes to the system at the same time, but it did work for me.