Phalaenopsis with white spots on leaves

[AEKass]

I just noticed white spots on many of my Phalaenopsis's leaves. I am wondering if these spots are due to disease or sunburn. The plant already has a large sunburn on one leaf (from several years ago). If it's a disease, I'm not sure what it is since the spots are white (at least for now).

I recently re-potted the plant. The photos are of it in its new pot. The medium is Phalaenopsis Monterey Dark Imperial Orchid Mix by rePotme. It had been in a room with south and west facing windows--all windows have shades. I have a smaller Phalaenopsis in the same area, and it does not have any of these spots. I moved the one with the spots to my living room/dining area, which has north and south facing windows, but is less bright. For reference, I live in northern California (Bay area).

The roots look healthy, and it has a new spike.