Dendrobium striclandianum - yellow leaves

[Vina]

Dendrobium striclandianum I have a little more than a year.At first it did well. But last 3-4 months it looks poor, unhealthy.
Two canes dropped all leaves, rest of them hold leaves wilted and pale; without turgor and sheen.
Roots look good.
There are 3 new growths.

Any recommendation would be very appreciated.

Growing conditions:
E facing window
humidity ~45-50%
temp Daytime 65-70 F
Night 60-64 F
~12h artificial lights