Discus Problems with Questions

To start, this is my thread with my stock including pictures.

http://www.monsterfishkeepers.com/forums/showthread.php?t=396026

Ever since I got these discus about 3 weeks ago, the blue one has always acted very timid and for no reason at all sometimes with hide in a corner and change his colors. The blood pigeon is doing great for the most part.

Since I last updated one of my apistogramma (the less colorful one) has died, but that is the only death.

Besides the discus, ever fish in the tank does great. The water is kept between 80-83 and I feed frozen blood worm, beef heart and brine shrimp.
The blood pigeon for the most part eats very well. In the last week though the blue one with swim under a rock and hide until I am gone which I do not understand. (I later noticed that this one has a slit in the top of his eye. Like a ( but facing downward on top of his eye. I later read this is something to avoid.)

I have also been doing 20-40% water changes every other day, and for some reason during and after the water change the blood pigeon will sit in a corner, breathe heavily and for the most part not act wonderful. His colors will stay great but his actions display how he is feeling I guess. I dont really understand why, please give insight on this.

Now here is the real problem. Now I know if conditions are perfect this should not be a problem for discus but last night I notice maybe 10 speckles of what looks like to be ich on the blue discus who is always stressed. What I don't understand is how he can look beautiful sometimes, then drastically change his colors and hide. Even though he has ich, when I came down to check on them this morning he was swimming around with the other discus, but is very dark (almost black).

I put an additional 100w heater in the tank to help stabalize the temperature at 86-88. I also already have a very large air stone for aeration. Should I take any other steps and does anyone have any other advice on my troublesome discus?

I know this, but the common problems that come with not having 6 discus (picking on each other) is not happening. Just the healthier one looking stressed after water changes (he is eating fine) and the blue one hiding when I come near tank, not eating regularly and him just getting ich.

The one healthy one (blood pigeon) practicably eats out of my hand. The other one hides during this.

I guess you are right. I do not notice any aggression or "picking" though. No fins are frayed or anything. Just a stressed fish. It is weird because the blue one will look beautiful swimming with the blood pigeon, then for no reason will scurry into a corner or under the rock and turn a very dark purple almost black. This prolonged stress has caused ich, and I just hope it doesnt last long.