Good advice from Gage regarding the heat, even though these orchids are from the hot tropics, they are not used to the 'dry heat' humidity is the key. In my greenhouse every summer temperatures soar to around 110-112 F but the humidity stays close to 98% thats why my plants remain mostly unaffected the same temperatures without the humidity would dry them out completely in 2 days or so !! With high humidity comes the problems associated with it like rots so to balance that you need good circulation. So its just not one factor light, heat, humidity and circulation are all intertwined. And lastly Vandaeceous take a beating after repotting especially if done at the wrong time, it will take some time for them to take off.