Flat and reddish phalaenopsis root tips under LEDs

[cantrell]

Hi, all. I'm trying to grow some phals under LEDs. They're doing fairly well, but I'm not getting the really long, plump, pointy root tips I was hoping for. Instead, root tips start out very green, pointy, and long, but end up red/brown on top, and somewhat flat.

Roots that grow in the shade of a leave are perfectly green and perfectly shaped, but when they get into the light, they darken, shorten, and flatten out on top.

I've attached the following photos:

1. Close-up of root tips.
2. All the roots on one of my phals.
3. A new root on a mini phal. Notice that it's very green, but starting to shrivel and turn red/brown.

Is this an indication that they're getting too much light? Here is a breakdown of my growing conditions:

• 1,500 foot candles of light.
• Main lights are 6,500 Kelvin with some 2,700 K supplements.
• Lights are on according to the season (14 hours in the summer, closer to 8 in the winter).
• Between 50% and 70% humidity (depending on the season).
• Temps between 70 and 77 degrees.
• Medium is lava rock.

Any thoughts?

Thanks,
Christian