I don't think I've ever fertilized this one, only tap water. Mineral buildup seems likely; another plant (that I've never fertilized) a few months ago started getting burnt leaf tips so I've been working on watering better.

Nice to know that this one doesn't seem on track for an early death!

I agree just spots I have a mister that goes on and off daily and I sometimes get spots I believe because the mist sits on the leaves. Not a issue on the plant they bloom and it does not spread to other types only the soft thin leaves seem to get them by times.