Yes, it sounds like the usual humidity deficit. What does not help is that I certainly think you feed too much and probably impede the plant's water intake at the roots as well- due to salt buildup in the rooting medium... your flushes are too infrequent. Feed only every third watering. But first I would repot into fresh medium.

I have not grown this particular Epi but I have found Epidendrum and Encyclia / Prosthecea orchids are among the orchids that can be sensitive to marked fluctuations in humidity, showing deformed development in leaves and blooms. I try to avoid the roots drying out too much between watering and this prevents the problem from reappearing. (But there is one Epi/Enc hybrid I have that conrinues to disappoint, so I do sympathise!)

I really hope your lovely plant gets well.