Brassavola Nodosa Sunburn or Fungal Infection?

[Pinkeed]

I got this orchid from lowes a few months ago. It was in pretty terrible looking bark, but still managing to grow a bit. I moved it to lava rock in a net pot. I grow it indoors and it gets full sun from the balcony. I'm worried that it might be fungal since it seems to mainly be at the top of the plant. No other plants are affected. Plant is watered every 2-3 days.