All coral and even sponges release some toxins. Either to take over valuable reef territory or to ward off predators or both.
I have no personal scientific proof but I observed my staghorns die off the same time my blue mushroom population exploded and covered almost all of my live rock.
I now have two separate tanks and the blue mushrooms play well with all of the soft coral in my tank. Eventually they will fight over rock to grow and one will win but it won’t be a catastrophic decline like with SPS. I currently have zoos, shrooms and numerous other soft coral either touching or very close on the same rock and have noticed little decline of health of any party.
Lots of carbon, lots of skimming and maybe ozone will keep the toxins at bay.
Bill