Chris, if you don't mind, un-pot that one on the center-right, the one with large, but yellow leaves. While it is un-potted, examine the roots and tell me what you see. Examine the undersides of the leaves. Anything of concern there? Then dump out and describe the potting media. Is it loaded with moss? Is the bark broken down? Does it appear to be water-retentive? Are the drainage holes large and open?
If I had orchids that looked like this, I would be very concerned. So much yellowing is simply not normal or good. I looks to me like many other plants' leaves are starting to turn color too. I almost commented on the leaf-color in that first picture, the one with the flower, but I simply thought it was the lighting that caused the coloration.
Report back. We'll get this figured out.
