Ok, first things first, is it sitting in water? What is the airflow like? How is overall humidity? This looks a bit like a fungal infection, but it also looks like a small case of sunburn. Also your leaves are looking a bit shrivelled, as a re the pseudobulbs, so perhaps the roots system is severely damaged and cannot draw water?
If you think it is sunburned, move it into a space where it gets morning sun, its always the coolest. Either that, or keep in very light shade. I would also lay of watering if the media is staying wet, or if it dries quickly, water more often.