Naked Denrobium Spectabile!

[Lucinda Brown]

I have a 3" Den. Spectabile that did great all summer and was put in my new greenhouse, did great there,also,until about a month ago.I went out there one day and the leaves had almost all turned overnight[maybe 2] to yellow.No sign of mites,etc. It lost all leaves but has what I believe is a new growth or keiki coming out of one cane.I know den's are prone to losing leaves in winter,but all of them? Did I do some major league wrong to it or is this normal for a Den. Spectabile? I have many other denrobiums that have lost a leaf or 2, mostly on older previously bloomed canes but have never seen one lose them all except in my true 'newbie' stage when I overwatered and they keikied. Is there any hope for this guy? Help!