You're right on schedule... that's all part of new tank syndrome! There's a reason that many of the more delicate livestock is recommended for tanks over six months old. It really seems to take the first six months for the biochemistry of the tank to stabilize. And I personally think a tank doesn't seem to reach its "sweet spot" in mature growth, flourishing, etc. until about a year.

So the good news is that you are coming up on some good times ahead!