Yes, it would be beneficial for your fish to do daily wcs for a week or 2 if it's not to burdensome for you.
It will do nothing but good. After that 3 or 4 wcs a week would be excellent - you could get by with 3 a week since your fish are near adult - so don't be too concerned about it. But do it as regularly as you can, with a substrate vac each time, and I believe you'll see a change for the better in the look and behaviors of your discus.
And you could reduce the temp to 82 - that's very satisfactory for discus - I keep mine @ 82 all the time. No need for as high as 84, and a lower temp could be better for your ghost knife fish.
It will do nothing but good. After that 3 or 4 wcs a week would be excellent - you could get by with 3 a week since your fish are near adult - so don't be too concerned about it. But do it as regularly as you can, with a substrate vac each time, and I believe you'll see a change for the better in the look and behaviors of your discus.
And you could reduce the temp to 82 - that's very satisfactory for discus - I keep mine @ 82 all the time. No need for as high as 84, and a lower temp could be better for your ghost knife fish.