Small white flecks on my dendrobiums?

[mam288]

Can anyone identify these small white flecks on my dendrobiums? I have them on several plants, there seem be more of them around the 'joints' (for lack of a better word, I'm not sure what the correct term is) in the canes and at the base of the leaves. They don't seem to move, but they came back after I washed the plants. Also, the leaves on some canes have dried up and turned brown, which I think might be connected.