Two ponderosa pines and a blue spruce have brown needles with black buds and the sphagnum moss and green moss surface treatment has turned black! I have moved them into quarantine and treated with fungicide. Any help or suggestions would be appreciated. Not confident they will survive but want to protect other trees. 
Hi @Bonsai_bob
Do you have any pictures?
Acid will kill moss quickly. Where were the pots situated?
I had a similar problem once, turned out it was cat pee.
Placed on stands on a raised deck with 6 to 8 hours sunlight. No cats at our house, but woodland and prairie surrounding us. I have removed the moss covering and reduced water to see if they will recover.
believe they are lost.
Not good. 
Autopsy time to try to find out what has killed them. Certainly something more serious than cat pee. Please let us know what you find.
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