If it were mine, I would keep it in a room away from the others and observe it. It could be some sort of fungus but it could also be viral. If it is a fungus, it will grow and bloom just as vigorously as it always has (or should) and you will not see any color break or further issues.
I took a Cattleya to an Orchid Society meeting once and someone jammed another Cattleya, with obvious color break on the flowers, against mine. I put it in another room when I brought it home. It always had put out new growth and bloomed like clockwork and, after the exposure to mosaic virus, it was late putting out new growth (the leaves developed a pattern), then very late to bloom. When it did bloom, the flower was slightly deformed and had color break so I knew...into the trash bin it went. When a plant succumbs to virus, there is a loss of vigor...which is why many plants are being bred to be virus-resistant.
If you have not had the orchid for many years, though, before you know it was exposed, it might not be quite so clear that is losing its battle to the virus. In that case, it is best to test it (twice to make certain that there is no error, or send the samples to a lab to have it professionally done--Critter Creek). But, in either case, keep it away from your other orchids and wash your hands and anything else that touches the plant very well after you touch that plant. Mosaic virus spreads easily. Funny enough, though, some study showed that coating plants with milk can help prevent plants from being infected by contact (sap touching unhealed wounds, though, will definitely allow mosaic virus an entry point).
This is a link to diseases to use as a guide:
https://staugorchidsociety.org/PDF/O...ySueBottom.pdf