You have the right idea with the tank lay out if your were raising Sub Adults/Adults! But, in this case you are raising Juvies and only 3 at that. You really should have a minimum of 5 or 6 Discus in your tank just to ease the stress... They are schooling fish! Juvies require multiple feedings and CLEAN PRISTINE water which requires lots of water changes! You do that for Juvies so you achieve a MAXIMUM growth potential and a healthy stock!
it does look like the fish you have are stunted! Based on the body proportion "Football shape" and The large eyes!