LPS corals receding

[iamfrontosa]

Reducing your light level is the right step, IMO.
How deep is your sand bed? If cyno keeps coming back, maybe you want to remove some sands, go bare bottom or just keep a very thin layer of it for decorative.

You don't really need to dose all those chemicals. Turn off the light for a few days while cyno is making a come back is better.

Once that's under control, hopefully LPS receding will stop.

My two cents.