dendrobium bracteosum brown spots on leaves/dark sheath

[Calbears]

The first picture of this den. bracteosum shows the newest cane which in the last day or two is showing some brownish /red spotting on the edges of the new leaves. It's a little blurry as I took this photo with my phone, I'll take another with the dslr later and post it. The second photo shows one of the older canes which has developed some darkness and I'm worried it may be rot. A leave turned yellow and dropped from the top of that section a couple weeks ago. I'm new to orchids in general and this species in particular so I'm not sure if this a normal progression.

Thanks for the advise