You need to get your nitrate and phosphate numbers off zero. Feed your aquarium more and it will happen as a byproduct of feeding. You also want to keep your parameters stable, meaning without swings.
Yup, bottomed out nutrients starve corals and activates dinoflagellates. Brightwell neophos for phosphates and neonitro for nitrates will help you keep ‘em off zero if your feeding schedule isn’t keeping up. Or feed heavier. Only problem I have with feeding heavier is numbers can get away from you if you’re not testing regularly and it’s harder to gauge how much nutrients you’re putting in.
Also, if it’s still on the frag and not mounted. It wouldn’t hurt to dip it in seachem reef dip for about ten minutes. The iodine helps sooth the coral and knocks off pests that may have snuck onto your coral.