The problem with bad habits in horses is that they can take a long long long time to change, and that there are small things that you can do to confuse a horse when training them. With horses, it can take 30 - 50 times of repitition to make them learn and understand, which is why when doing things like breaking them in, you'll put your foot into the stirrup and take it out over and over and over until the horse understands whats happening, before you even attempt to put weight in it and get onto the saddle.

The best thing to do would be seperate them if you are working them both. Have one someone else and spend time one on one. Start with the QH. I'd work with one of them full on for a while, not go between the two. Dedicate a fair ammount of time to that horse for now. Is there someone more experienced at riding who could do some work with him??