Sorry, but I have not had a tray become useless yet, but check out this thread where I had a clouded tray. That was just from the pigment settling and was fixed by lightly scraping the base layer of the tank with the putty knife.
Unless you have more than 2L of resin printed on a single tank, I doubt that the clouding is the issue. I just started my 3rd bottle of black resin on one of my tanks, and it is still printing nicely.