I would not carbon dose and simply monitor corals. If coral growth is lacking maybe adding a little ammonium might increase growth. However, imo, if you do add ammonium and growth improves, I don’t necessarily agree that ammonium is the reason. I notice subtle changes in my aquarium all the time and don’t change anything. Things are constantly evolving in my aquarium that I have no real explanations why. Here is an example from ICP testing, manganese seems to bounce around, maybe this could explain some changes or maybe it’s testing error or maybe nothing? Note the graph over the last year of testing.