Scalding Under Artificial Lights? or Disease?

[flowerchild]

Hi All,

I am new to this forum and am desperate for some advice from you experts!

I have been growing orchids for quite a while now and about a year ago was forced to move my collection under artificial lights when I moved to an apt with a north exposure. My setup consists of several shelves, each with 2xT12 and 2xT8 full spectrum lights (from Verilux) which are on a timer and run for 12 hrs a day. I have a space humidifer in the room to help with humidity.

I was under the impression that you couldn't burn plants under artificial lights but over the past 6 mths or so many of my plants have developed what looks like scalding on the leaves. (Yellowing splotches which eventually turn to black spots- sometimes ending in loss of leaves.) Sometimes the psuebulbs even have the marks-but they still flower.

At first I panicked, when I saw the black spots-thinking I had a fungus or a virus running rampant through my collection so I started repotting and soaking/spraying with Physan 20. But it made no difference. Now I don't know what to think...

Among those affected include my vandas, dendrobiums, oncindiums, and some of my catts. Almost all of my vandas have flowered despite the splotches and many of my oncinduims with the splotches have also flowered....I've had no success with the catts.

I have attached a few pictures of my setup and the splotches on various affected species. Any help/opinions you have would be greatly appreciated.

Thanks! (Please excuse my terrible spelling!!)