Dont mess with water parameters. Stable water is the most important thing with discus. Tank bred discus like the ones im assuming you have are tolerant to a large range of paramaters. Twice daily 50% water changes are fine but really all you need to worry about is removing old uneaten food. With a barebottom tank I dont think 50% is necessary, and with full grown adult discus like I think you said you had you really dont need a barebottom tank. People use barebottom tanks for growing out juvinilles. Only juvies require daily water changes and heavy feeding.
If they are in a new tank just leave the lights off and let them be for a few days. Discus are always skittish when getting used to a new tank and need time to be left to acclimate. Just leave them alone for a bit, quit sticking your hands in the tank and chill out dude. I had one Discus that took a week before it stopped hiding in the corner while the other 4 were happy as clams. He came around now and is still a bit more skittish than the others but not nearly as bad.
BUT, if you plan on breeding your fish it probably wont happen unless you use RO water.
