Alright, changing filter media weekly is a bad idea, you remove most of your nitrifying bacterial colony right there. Cleaning and changing are different, cleaning is just as it sounds, you take tank water, rinse the filter material out and return it to the filter, hard to do with carbon and peat, but I don't reccomend either anyway.
Carbon is not that great of stuff, I never reccomend using it unless you need to remove a medication, even then water changes are a better way to do that. Some filter wool, bio balls, or Siporax ceramic peices would be a much better alternative.
Peat as a substrate, not a good idea either. Discus DO NOT need soft acidic water contrary to popular opinion, they will do find in hard alkaline water straight from the tap. The peat breaks down and releases other things into the water as well over time.
I agree with Anona about your water, and is what I was suspective of. The quality of that water is substandard for the discus, which is why they exhibit the jumpy behavior. I would reccomend at least 3 50% changes weekly, spaced out evenly during the week. Water temp around 84-86 is also best.