Hi Ksermie,
It seems like you are doing everything right. Your problems are likely traced to that ammonia spike. There are a lot of threads about mysterious discus illness here. And, medication often doesn't help. Once they have trouble, there could be a cascade of problems.
I am beginning to think that discus (especially wilds) can have a residual effect from stress. Mad dashes around the tank appears to be the big warning sign even in otherwise healthy fish. Really, the best thing that we can do is probably to FIRST buy only healthy specimens and SECOND always retain quality water. I am sorry that in your case the horse is already out of the barn, so to speak.
Personally, out of twenty discus that I have, one is a dasher. I thought he was done for yesterday but this morning he is still alive. I believe this fish is the same one that nearly died after being delayed by our last ice storm. None of my other discus are dashing. I think it's troubles are due to almost dying in shipping.
So, it is probably by far in our best interest to avoid problems rather than address them. Keep up the quality water. However, if I were you, I would start aging my water for a day or two. Your pH may be swinging too much at a water change. Many here (including myself) have made problems worse with a lot of big changes consecutively.
I wish there were more concrete answers. The best discus keepers here never allow their fish to be stressed to begin with. They never end up chasing their tail.
I really hope everything works out for you. I have been there. Live and Learn,
Andy