D. Stardust 'Firebird' Leaves yellowing on new growths

[Tango]

Hi everyone,

It's been a long time since the last post!

I have a Dendrobium Stardust 'Firebird' that was already starting to grow. New canes looked okay until several days ago, when I started to notice a dark mottled pattern followed of leaf yellowing and eventually leaf loss.
What could it be?
I have the plant for 3 years and seemed to be (more or less) okay all the time.

Thanks!

Tango

[estación seca]

Be sure you don't have spider mites. When my thin-leafed Dens look sick I spray them with soap solution or alcohol just in case there are mites I can't see.

How are you watering? When did you last repot it? How do the roots look?

[Tango]

Thanks Estación Seca

The plant is in a small basket covered with Sphagnum, I keep it moist all time, and the roots look okay. It was starting to grow quite strongly after blooming but suddenly started to get sick.
I'll give it a good bath with baby shampoo.

I have other dens: several nobiles, aphyllum, loddigesii etc but this one is specially finicky.

[estación seca]

That story sounds like spider mites or a sudden hot spell.

[Tango]

Maybe some invisible mites, I hope soapy water kills them.
I wish they were more robust.