Help.....SPS coral is dying off. SG is low.

[newreefer_59]

Have SPS coral (brown montipora and hydnophora) that has badly deteriorated the past few weeks. my LPS coral looks good and the fish look great. I have had to move out of my home as of last July, and the tenants have cared for the tank and I have done the water changes up until last month. Now, the tenants have done them too. However, she was not adding enough reef crystals as the SG level was only 1.021. We did a change together and raised the SG slightly and will continue to raise to the 1.025 area. Calcium was 420, Ph was 8.7, but KH was 10. Would the SG level at 1.021 cause the demise of this coral?