I would consider keeping it away from your other plants. It wouldn't be sunburn under those lighting conditions. Did it have the marks when you bought it? If it was in bloom, were the flowers streaked, which can indicate virus as well. It looks healthy otherwise, but they can be virused and look healthy. Hopefully someone else will have an opinion. You should see if you can Google some photos of a virused phal. I don't know what the patterning would look like for sure.
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