Hi and welcome too!!!! A couple of things....The landscape looks good just watch for rockslides. As to the partial changes at this time, it looks from the numbers, that waiting for the cycle to finish may be more of why things are out of whack. More patience is always what many of us need in this obsession. Was that calcium only 250?? Not an issue with an empty tank but should be 400 or so with corals. SPS ans softies at times together make issues too. Others may pipe in on probles here. Ohhhh, what is the lighting and tank size too??
But I saw that you want to add a Mandarin. Yes they are beautiful fish, but the tank should be up and running for 6 months or so to establish a stable pod population to feed it. Too many folks buy only to watch them slowly starve with newer or too small or setups. Also watch out with having more than one Angel fish can be a problem too. Most are only one to a tank............ Good Luck...........