Hey fellows it's been a week now since I took out my sandbed and everything looks stable again. I Haven't had any losses since then or tissue loss and the corals are opening up nicely again and coraline algae has been growing quite a bit. Some of my corals which I thought were dead are actually showing little bits of colour on some branches as well so I might be able to save them.

I can't really pin point the loss on anything other than my sandbed. The water was quite dirty in the bin that I siphoned all the sand and detritus into but I dont think it could have been the detritus traped in the sandbed that caused this because my ammonia nitrites nitrates phosphates alays came up as 0.

All i can think of is if the power heads were blowing the sand around which caused hydrogen sulfide to slowly release into the water? I think carbon neutralizes the hydrogen sulfide but maybe it was a steady slow release? I'm stumped...

This barebottom thing takes some getting used to but I think it's growing on me :mrgreen:

Thank you everyone for your help!

Glad to hear things are improving.
One thing to keep in mind, depending on how old your live rock is, it could be contributing an extra amount to your detritus buildup through a process called bacterial turgor.
Basically, turgor is when the pressure builds up in bacterial cell walls and forces waste products out.
The bacteria in the top few millimeters of your live rock could just be cleaning out the old live rock.