Hi,
Last year i bought a Den. Horny Burna with one mature cane, and one that was developing. After the new cane matured, it dropped all of its leafs, which was very strange to me.
now, it started developing another new growth, but i already see one of the leaves turning brown.
Happens frequently with this group of Dendrobiums.
Be careful of your temperatures, water regularly (but don't grow them soggy), and be mindful of their root health. Also, try not to get water into the crowns.
I have one that's much larger (Den. Antler Hybrid Purple), and I'm having a similar problem. My leaves are turning yellow, shriveling, and falling off. Not all of them of course.
King_of_orchid_growing - When you say be careful of temperatures, what do you mean? I'm growing it in my house, but suspect that the AC may be the problem. I live in Houston, so summer can be pretty brutal. However, if they like it hot, then I can certainly provide that.