Putting the discus in that tank is not a smart idea. First a 30 is really only big enough for a bonded pair. The fish you have in there currently are not suitable tank mates for the discus. As to the water requirements that have been listed for the discus, BS. They do not NEED soft water, Juvies grow much better in hard water. There are two very big factors with discus, frequent water changes to maintain high water quality, and a warm temp. Many breeders grow their juvies out in hard alkaline water because the finnage is better on fish grown in such conditions. Simply put, SOFT water only comes into play when attempting to spawn the fish. In water with TDS above 220ish you will not get much for a hatch out if anything, idealy you want a TDS down around 100 for a good hatch.
Water changes need to be done daily to every other day with Juvies to maintain good growth, and the water temp should be kept around 88 for juvies until they reach 4.5-5" where you can drop it down to 84-85. You need to do many feedings with young fish as well, on the order of 4-6 daily.
As to juvies having small stomachs, yeah right.... that is not true at all. The frequent feedings are because discus have a high metabolism when they are young, naturally they are "grazers" which feed all day long. Simply put the more you feed them, the faster they grow, but the more water changes that need to be completed.
For your first go around with discus, a 55gal is basically minimum, if you are getting young fish, bare bottom, with a simple sponge filter is what you should go with. Why? Bare bottom is much easier to clean, suck debris off the bottom and wipe the tank down at each WC. Get 6 juvies and start from there. Discus feed much better in groups especially when young.
Here's a link to a home-made food mix I make. I feed only this except with some Tetra Colorbits occassionally or Brine Shrimp.
http://www.cichliddomain.com/forum/viewtopic.php?p=96&sid=1eba4db50a1decdac89e96c36734249d&no=1#96
Here