Help! hybrid Mtssa x Odm Bictoniese leaves dying

[juls54]

I was given this orchid as a gift and about two weeks ago the leaves started turning yellow and now have light brown areas. It is kept by a eastern facing window,generally have 40% humidity in house, 70 degrees during day and close to 60 at night and I keep ceiling fan going all day. I water about every 7 days. I also have another hybrid orchid of about the same variety that is doing wonderful. I don't know what to do. Please help.