dendrobium eximium new growth keeps rotting

[musamusa1975]

Hi everyone,

I've had this dendrobium eximium for about a year. It has sent up about three new stalks that have all rotted on me once they get about 6 or 7 inches long. The rot seems to start in the middle of the stalk. The very bottom and the very top seem to be green and healthy. Eventually it collapses. I've got two new growths forming and I'd hate to kill those also, so I'd appreciate some feedback on how to grow this better.
Right now, it's in my bathroom. It gets bright indirect light most mornings. Daytime temps (at least now in the winter) are around 69-70. Probably around 65 at night. I was afraid I watered it too much causing the rot, so I've been watering about once every 1.5 weeks or so (when I see the bark look a bit dry).

Thanks in advance for your help!!

Michael