I suspect it's a case of dehydration. Aside from semi-hydro, I've never heard of self-watering pots being used for orchids - and semi-hydro doesn't use standard self-watering pots. If it's one of those glazed clay pots that has an unglazed clay insert (commonly called "African violet" pots) then you're drying your orchid to death. Remove the plant from the self-watering pot, cut off any and all dead roots, and put it in a normal plastic or terracotta pot. Phals require consistently moist medium, and shouldn't dry out completely.
-Tim
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