he's a feed monger, that lighting is sufficient more light wont do it.
100% for sure, if you spot feed him three times a week in a/m when polyps are out and sustain that 4 mos/extra polyps come about. my personal ideal feed for my same coral is roti feast and roe eggs from reef nutrition, mixed together. its one of many avail feeds, but it happens to be a set of feeds that grows my coral really well without making excess nutrients in the tank. they're my go-to's now.
Mysis and other things work, but you need to grind them up so the particles are easier taken in, these smaller corals tend to regurg most of the whole shrimp they take in an hour later. the roti feast/eggs are already tiny and they are retained well
you have options such as occasionally placing a tiny inverted plastic cup over that frag as it sits on the sand, and injecting a day's worth of refrigerated feed you'd normally put into that tank all into the cup for the corals 1st picking
then release the cup an hour later, tank is fed like normal with nothing extra added but he got all first take
little tricks that way w work
B
even if you don't feed him I can tell by the details in that tank pic he'll grow just fine over time only much slower, which is ideal in some scenarios like small tanks w no room. your system feeds him well, but spot feeding/cups etc is turbo