Icy problem

[Kelvin]

I got icy I brought down my salinity 0.1009 waited about 7 day started
To raise salinity after the ich was gone my black damsel became white
And my blue Atlantic tang goes back and forth very fast all day and his face
Goes white some times I don't no if the ich has come back if so should
I lower salinity again ? I have corals and live rock I took corals out and invertabries I'm worried if my live rock will die with the low salinity what should I do.