Dendrochilum brown leaves

[bdublyou]

I recently purchased a Dendrochilum willamsii, the plant arrived looking pretty good with a large number of growths and a large healthy root system. When it arrived there were some leaf tips that were slightly brown on the ends and several others that appeared to have been clipped at the grower (presumably removing browning tips?). Anyway, since I've had it (a couple of weeks...) probably about ten or so leaves have started to brown on the ends and slowly working down to the leaf base. I have it indoors where the temps are consistently hovering between 72-76 F with no significant dip at night. It is growing in a north facing window with a bunch of happy Phals and a Christmas Cactus. It is planted in live sphagnum in a net pot over a humidity tray and placed near an open window for airflow . I water fron the bottom to keep it moist but not wet...typically about once a week. I heard that some of the other species can have a significant leaf drop in the fall and after flowering. It does seem like the browning leaves are older...being longer than the rest and some having spent spikes. So, question is, is this likely a normal leaf cycle for the plant or does it sound like I need to tweak the culture? I understand it is very similar to tenellum.