I use salifert for the calcium, magnesium, alkalinity and phosphates. Unless I use the hanna checker for the alk
The ph is fine too, if it consistently stays around the same number it is better believe it or not to just leave it than to mess with it. I ran for years at 7.8 and never had any issues with corals. Over the years it has kinda adjusted itself up to like 8.3, go figure. lol
But yeah, get good accurate tests and let us know what the readings are over a period of say a week. That will really shine a light on what is going on in that tank.