I've grown and flowered them in CHC based mixes, but these plants are presently in a bark mix. Also the quality of CHC varies a lot from source to source. May be too many variables to blame potting mix or water quality. Humidity is good.
They could probably appreciate lower light levels, and maybe a shorter day length if you don't modify it during the year. Obviously the plants in my GH are in dark or very dim from 4-5pm till 8 or so AM right now. Thats only 8 hours of decent light. And since they are in the back NW corner under a lot of hanging plants it's pretty dim most of the day during the winter for mine.
What is your low end temperature. If you are indoors maybe they are not cool enough during the bloom time. I'm getting down to around 60 at night, and with a cloudy day outside I doubt if I get above 70 right now. I used to run night temps into the mid 50's but have raised up a little for my Bulbos and Phals. Rick in TX is running in the high 50's at night.
Unless you are doing things indoors to make a dark cool period, they may be blasting from lack of seasonal cues.
