This conversations page is not the place to ask orchid culture questions. Much more activity over on the discussions page including many discussions about problems with Phalaenopsis.

Could it be that all the canes are getting old and woody--old canes don't bloom as much as new ones, which is why books will tell you to remove some old canes to make way for the new ones. I did this at the end of winter--we are getting lots of basal breaks to replace the old canes. But, your climate is much different--we have winter damage to deal with. I've noticed our OGRs won't put out vigorous new growth unless pruned hard--they don't have the winter damage issue. But, most of the OGRs we grow aren't suited for warm climates.

When I first started growing AVs, I recall reading a similar thread. The wise people suggested that there different plants have different bloom cycles. Some, they contended, bloom only twice a year, each time sending a mass of upward blooms. Others tend to bloom every couple months for a month or two, then take a break. And, the rarest tend to bloom relatively continuously, taking short breaks now and again. These wise people suggested doing all the "right" things as the Stork article suggests and then just being patient. After a year or so, you'll know the cycle of the plants you have and will know what to expect. Xuan suggested changing the soil. Did you repot them when you received them? If there are too large of a pot, they might stop blooming to grow roots. Or, if they were not repotted at the time, it might be time for that, especially if they are still in the all peat (heavier than most of us use) soil mix that is often used by nurseries. So, you have many options to try! Good luck and hope you enjoy working with them even if they are not blooming yet.

My 4 foot variegated brugs drop leaves as well. They've done that since I first had them 4 years ago. I accept that this is one of their characteristics. You mention that it is the largest ones that drop. That makes sense to me. Mine are constantly replenishing the leaves once they are not working for the plant as efficiently as the newer ones. LOL That sounds like my skin. Be sure that it gets lots of sun. I find that mine like the light. Also be sure that it gets good drainage. The plant likes water, but doesn't like to be soggy. I fertilize mine every week. Last year I had 175+ blooms at once. They have just gone through a flush that is close to a 100 blooms.