Kelp extract and deciduous dendrobiums?

[Libo]

Hi! This is the first time I post on the Dendrobium board, since I don't have a lot of dendrobiums in my collection. But there is something interesting I'd like to have opinions of experts on.

I recently read some posts about kelp (seaweed) extract and decided try to give it a shot, thinking how could it hurt anything? Well, I tried with the supplier's recommendation strength with just one spray (I can't believe how dark the liquid is...), and magic happened. Most of my other plants, namely catts, neos, phals react quite positively with immediate appearance of root growth. However, almost all my dendrobiums (mostly deciduous species with one or two evergreen type) had their older leaves turn yellow immediately and started to shed like crazy. The weird thing is that the pseudobulbs are quite plump and green with no sign of dehydration at all. My dendrobium unicum shed all of its leaves while dendrobium laevifolium and dendrobium aggregatum shed their old leaves with new leaves perfectly green. The new growths are showing root growth as well. I wonder what is causing this phenomenon. I don't think it is a coincidence that one day I sprayed the kelp extract and the second day winter came. Is it because I kept the plants too warm so they kept their leaves a little too long than they would do in nature but the kelp extract hormone forced them to sleep now? They are in temperature ranging from 62 - 68 F right now. Some of my terrestrial cymbidium species also showed fading of older leaves as well, in contrast, some of my catts and phals actually turned into a darker green. I am so confused. Is it a good thing or bad thing for the plants to drop its old leaves...