Vanda orchid suddenly loosing leaves

[Blueszz]

I have to admit I keep mine at 17-20C too during winter, in front of a south facing window.

Mine do well, no leaf loss at all. I dunk the roots over night twice a week. Healthy roots.

Of course higher temperatures is want they want, but apparently they can tolerate the conditions I provide

V. tricolor, suavis, lamellatta and Vanda Pure’s Wax (Blue) (= V. Doctor Anek x V. Kasem's Delight). They even grow beautiful healthy leaves.