I would raise these juveniles in larger tank than 20 gal especially if more than two.
Young Discus will produce best growth, with thee to four feeding's per day, which in turn mean's more frequent water changes to keep metabolic input to minimum.
20 gal would not provide as much dilution capability as larger tank.
82 to 86 degree's is fine for temp.
Once the Discus reach adult size,,once or twice a day feeding's is all that is needed.
I might also visit SimplyDiscus.com for perhap's insight on other's who have done what you are striving for.