My Phal, that I got from a big box store has multiple brown spots on it. I am unsure why and was wondering if anyone had any ideas. Otherwise it seems healthy and has multiple spikes with buds on them. Too much sunlight? I honestly have no idea.
Doesn't look like sunburn ... maybe water sitting on foliage during chilly temps? Or, possibly water sitting on the leaf while in the sun during high temps ...
I would guess something like Sonya says. The damage has a very distinct edge, and I would guess is not spreading as it looks like it happened a while ago. I wouldn't worry too much, just keep an eye out to ensure it isn't spreading.