This is what I was going to say about the Alk not dropping after a dose. The alkalinity from AFR is produced after it is metabolized so you wouldn’t see a drop until another day or so after a missed dose.I believe the way AFR works is that it takes a few days to break down and become effective such that you wouldn't see a change after skipping a day until a few days later. Its why after starting dosing for the first time, you dont see an effect until a few days later. Someone correct me if I'm wrong.
As for suitability in a new tank I’ve used AFR since I first put in coral and my tank just 4 months old. All coral are growing and doing well. Only problem I’ve had was with dinos and unrelated to AFR.
Everytime I thought I had a “problem” with a coral it was back to normal in a day or so. I thought my alveopora was suddenly dying until I saw a clown eating pods off of it/around it and my hawk fish deciding to perch on it. Since both stopped it’s totally back to normal. My citrus zoas close up for a few days when producing new polyps but then open right back up.
I would verify all flow is still the same (no clogged pumps) and keep watching it. Do you have any fish that might be messing with it? No changes in light?