Like the other poster mentioned start Small. Get like 2 hermits, and astrea snail. See what they are picking at and adjust from there.
We all hit this point, and we all battle something through our entire time in this hobby. Whether it’s uglies, pest, nutrients, ph. Like I said you’re doing a good job your nutrients are in a good spot. You have the the thin green algae on most the rock that coralline will take over eventually. Just don’t rush in trying to fix the problem and throw five different things at it. That’s when we run into bigger issues. Small batch of clean up crew, ideally quarantined or at very least scrub the shells, and transfer method into different containers of water a few times. Clean up crew won’t touch it Manual removal new cheap toothbrush and brush of those spots. While siphoning for water change. Stay away from additives like vibrant for now.