I have six track heads with 6 LED bulbs from Orchids Limited. They are four feet from my plants and every single one of my phalaenopsis are in Spike and Bloom reliably. They are $65 a bulb and they last for many years. They are natural white light. They are a wonderful addition to any setting and actually very effective on phalaenopsis orchids. I got them from Orchid web. Online. I got them 8 years ago. And they are still going strong. Check it out. You won't be disappointed.

I will try to address a few things here. First, as far as the "lava rock" medium goes, it's actually a lot more bark than lava rock, it's a good mixture of both. Before my phals were in some hideous moss contraption as most of them are and I didn't know any better until a year later when I repotted them. The phal with the keiki wasn't doing so hot at the time but I wanted to keiki to grow more so that is could take roots. When I repotted my plants I put them into pots that have a TON of air holes so that they could breath. When I did this, one of the phals took off and the other (with the keiki) got a little better but never really did a heck of a lot of growth, just looked less sad.

As far as fluorescents go - I didn't realize that they would work as grow lights? I need the bright daylight fluorescents? I have a small apartment with not a heck of a lot of access to do much addition and only 2 (will be 3) phals. Just want to make sure I get the right stuff. I didn't think that fluorescents gave enough light? Also - just wondering if those lights that you use for S.A.D (season affective disorder) might have the same effect? I guess I also don't understand why one is doing quite decently but the other is struggling so much.

When I was using the rig (which I made out of PVC pipe), I tried putting grow-light tubes in one fixture and comparing the results from that with the cheap, ordinary full-spectrum tubes that cost half as much. After a year i could see no difference. Now, perhaps if the fluorescents were the only light source maybe it would have made a difference. I did get some natural light in the window. Phals really don't need a lot of light - they just need it for more hours than they usually get indoors from natural light. No matter how great your window is, the sun shifts after a few hours and becomes less effective. For just a few plants, you should even get the desired effect with a desk lamp. At the time I did it, fluorescents were the only easy option. Now, you should get even better efficiency with LEDs. Sure, one of those SAD lights should work fine. The 12 hours part is key. (With a timer , you don't have to mess with it)

As far as why one makes and one doesn't... impossible to say. But it probably goes back to long before you acquired it... one may have been healthier to start with than the other, either with better (or less bad) care by the grower, shipper, seller... or plain old genetics. Some plants, like some people, are just more robust than others.