Thought about discuss, but was concerned that the higher water temp would be too much for some of the other fish and the plants.
I've kept discus for many years - almost always in planted tanks @ 83-84 F and never had any trouble growing plants at that temp - all one needs to do is select those plants that do well in the higher temps - and there's quite a long list of them. Did you have a look at my pic above ? That'll give you some idea of how plants can fare. That tank had been set up for months when I took the pic.
As for other species of fish that are compatible discus tank-mates, many do well at discus temps including all of those I've listed above, as I've kept all of those with discus.
I believe I read mention of your planning to maintain, or were maintaining, temp @ 78-80 - so 83 is not a great deal higher, & perfect for discus.
And for those of you who may think otherwise, discus are hardy fish and not at all difficult to keep. You just need to make sure you're getting quality, healthy stock from a recognized reliable supplier source, and give them a little extra care & attention. What good aquarist doesn't want to do that, to keep their fish healthy & thriving ?
Should you decide to consider giving it a try, cowfish, I for one would be glad to help you out every step of the way.