Blue striped mush died

[ginger7286]

I had several heads of the blue striped mushrooms on one rock. Several weeks ago they began to melt eventually turning to slime and dying. I had had them for 2 years. What caused this? My water is:Amm-0, Nitrit-0 Nitra-8, Alk/DKH-3.09/9.0, cal-460, sal-1.026/34, pH-8.0, phos-0.50, Mg-1250. My water has been maintained at these params for quite a while. Any suggestion? I am not near my book of numbers but I think I have them right or near right. oh yea, temp is 78f.

Thanks,