You certainly could have read Braem, Baker and Baker, but your question seem to indicate, that you might have forgotten the content of their text concerning rainfall, humidity, rest periode, etc.
OBS. Notice it's not the excellent books on Paphs with Dr. Braem alone or with other co-authors, I'm reffering to! One of the Baker couple, I think it was mr. Baker, was a meteorologist, hence the priceless, detailed information on the climate of the habitat (it was a sad thing, that they had to stop the planned 3 volume work after vol 2, due to the death of one of the Bakers).
The 2 vols are long out of print, and might not be the easiest to get hold of. But there is a website, where you can get hold of the information by the Baker's (cultural sheets for the different species from their books). I haven't, yet, tried the site, but soon will have to for the couple of Dendrobiums in my possesion:
https://orchidculture.com/COD/index.html
PS. Most of the above was primary meant as general Information.
I must say though, that your 3 druryis look very healthy and very well grown. So maybe you just need to simulate the climate of the winter monsoon: cut down on the watering a bit - lengthening the interval between waterings, but mist the plants once in a while (if the plants start to show signs of stress, due to lack of water, just water), and the Bakers recommend turning up the light in this periode, just to the point of almost, but not scorching the leaves.
I think, David might have been helped in flowering by the australian sun being on its way to its fullest at this time of year.
We so high up on the Northern hemisphere can't without some difficulties compete with that. My one time flowering of druryi came only in a year with heat wave and stark sun, that was already at its full fledge in the month of May:
Paph. druryi
