Patience my young padawan....... yes that was a StarWars joke.
I wouldn't call it unusual. This is one reason why you should have a good FULL set of tests. It's possibly you some some thing out of balance, which can affect this. Also, in this hobby 90 days is not old at all, I would barely consider it a new born. Yes your tank is cycled, however maturity and bio diveristy in your tank is very very young, and it will go through phases while it matures. Coralline will come with time, it needs to grow just like everything else in your tank. And just as reference, my tank is coming up on the 3 years now, and only about 6 months to a year ago did I finally call it mature. Things have settled in, everything is growing nicely, and with routine maintenance my parameters don't get too out of wack.
And back to my earlier joke, don't try to rush things by adding in useless chemicals, good husbandry and patience is the best thing you can do to keep your tank growing.