I'm not sure of the GPM on the two filters you have, but from what I've experienced after adding in wave makers to my 125 gallon is that the discus will inevitably come out of the corner and swim around the tank normally. Discus can be shy, especially in a new habitat. How long have they been in your tank and hiding in the corner? I'm wondering if they come out to swim more often when you turn off the filters and feed because it's more of the food is now in the tank rather than it being the flow from the filters is too high. Are they struggling to stay still in the tank as if they are being pushed around or what?