32 gallon biocube dosing advices

Hello guys, i've been runing my new led coralife 32 gall, for a month an a half now. I am using my old rock from another tank so thankful i didn't go through the cycling process. My concern is about dosing the tank, i have some corals now( small sizes) two frags of zoas, a hammer, GSP, xenia, candy cane, three head forge sponge, they've been doing pretty well. But they don't remain open all the time i don't know why the gsp and the candy cane are growing but the rest of them are not. I do a 5 gal water change every saturday . I am using the aquarium store water. Is it good or i should prepare mine at home? Please let me know if i am not doing something.

Calcium: 400
Magnesium: 1300-1350
Kh: 8 dkh
Nitrates- 0
No amonnia neither nitrites