I have worked with several different types of orchids and the number one killer of orchids is people leaving them in the same soil and pot they get them at the store. The store packs them in peat moss to hold moisture during their travel and the peat moss provides way too much moisture for the roots. Re-pot your orchid in a charcoal, coco noir, wood chips, and per-lite mixture. If it is not a soil medium issue then it could definitely be too much direct sun(orchids are not a big fan) or using tap water which can cause a chlorine build up and chlorosis in plants. If none of that helps, get a new one. Good Luck Friend!