Yellow spots and splotches on epidendrum

[KeyWestSunset]

Noticed these yellow splotches showing up on the upper parts of my epidendrum.
There is also a terete vanda with it. Which doesn't show the same symptoms. They've been growing on this board for probably 2 years.
Its been in full shade and full sun (gradually of course) in that time. Its been very neglected. I know it doesn't get watered or fertilized enough.
I also have had temperature fluctuations outside. For example last month one day its 85°F, then get a cold front rainstorm at night making it 52°F, then next day its in the 60's, then a day later it back in the 80's.
So maybe its environmental, or a nutrient deficiency? I'm hoping its not a fungus or worse, a virus!