Too much sun for this Catt. or deficiency?
 

I have a pot with a couple NoID cats in it, one of them turned red, while the others seem to be doing fine. It seems a bit dehidrated too. I'm debating if I should pull that one out, I'm afraid that they are too intertwined in there and I'll have to cut some roots off. I just hate disturbing them like that. What do you guys think?

One more

It is borderline too much sun.

Where and how are you growing them? You don't mention how much light they get, nor what sort of fertilizing regime you use. I know that in non-orchid plants reddening of leaves or leaf margins is often associated to phosporous deficiency, but here it's strange that the other plants in the pot are fine.

The pot is in bright filtered light. It gets quite bright around noon but its shaded by a large tree and huge ferns. Right now they get fertilized every other week with better gro bloom booster 11-35-15, I also switch it up with orchid plus, 20-14-13.
What is even weirder is that these orchids have been potted together for couple years, but only about 6-7mo ago this one started to red like this. The rest seem just fine. Hmm, should I try to take it out and mount it? Or is it going to just make matters worse for the already upset plant?

Could be the community pot that's the problem. Maybe it's getting outcompeted by the other plants and starting to suffer.

Can it be a Magnesium deficiency? Do you guys use Epsom salt when you fertilize?

Magnesium deficiency usually has symptoms closer to those of nitrogen deficiency (yellowing).

I supplement with epsom salts, but that's mainly because the tap water in my area has somewhat low amounts of magnesium. I had a new Phal which stayed really pale looking no matter how often it got fertilizer, and the moment I started the epsom salts it greened up again. But that was completely different symptoms.

You could try reducing the light for some weeks in case it's that, and if the red doesn't fade then consider repotting it separately.

Ok will do, to think about it these guys have not bloomed for me in a while. Hmm...

It looks like too much sun to me also.