I see similar tip issues with other succulents if they got too long wet then felt cold. Maybe lay off from watering a bit, it takes longer for media to dry out anyways during cold season. Oftentimes, I just leave tips that gets blackened alone, at times the blackened portion seals off the rest of the plant from further damage. I do not cut them off, just let nature take its toll. When Spring returns with its better temps, the succulents will bounce back.
My own epis are thriving outdoors in the cold, but I did have the plant by a cement slab, so maybe it is getting some passive heat dispersal at night. Luckily not raining for the past couple of weeks either, and I have not watered them at all, seeing the media gets the moisture from the air.
