Brown tips on oncidium with black spots

[alaina]

Hi,
I just recently started having trouble with my oncidium. One by one I have had leaf tips turn brown and get spots on the end. I thought maybe it needed more water, but the leaf shown here was green yesterday and I watered and then today realized the leaf turned brown. The last times this happened I cut down to healthy leaf tissue and put cinnamon on the wound. I would blame it on the fertilizer, but I did not use fertilizer yesterday, just tap water. I do not have trouble with 99% of my orchids with the tap so I don't think it is the water. Any ideas? Orchid seemed okay otherwise and just put off some new growth. Also, I did not water the leaves or the plant, just around it.
Thank you!