Problem w/BC Maikai x B little stars 'hawaii'

[ckollmer]

I have an established plant of this cross. Does great spring-fall. About this time of year, older leaves start to yellow, then drop off, even while new growth is coming on. I grow outdoors during warm months, indoors under HP sodium lamp this time of year. I grow many BLC & Slc catts and especially a lot of hybrids w/heavy Brassavola influence (B. little stars, BC Roman Holiday, Pot Hoku Gem, BL Morning Glory, etc) & do not have this problem w/any of others and treat all the same: ('Dynamite' fert., water weekly, good air movement, etc.) Night time temps are 62F, daytime 73F or so. I have tried cutting back on watering, increasing watering & neither seems to have impact. Plant has not bloomed yet and is in 5" pot size. Gets plent of light both now and outdoors in warm months. Any suggestions? Could it be result of cooler night temps?

[snow]

what,s you,re humidity?
sounds like you,re plants are too dry or too close to the lights.

[ckollmer]

humidity is > 50%. Not too close to lights - at least 4 feet away. [Plus Brassavolas are known to tolerate low humidity and bright light]. Any other ideas?