For discus, you need 2-3 things other than their basic requirements....You will need softer water below 100 microseimens (below 60 TDS/ppm), lower pH in the mid to low 6's (not required, but it helps a lot), and water that is exceptionally clean...one with a very low bio-load, meaning almost no bacteria in the water and VERY clean. The last part is next to impossible to do in a planted tank or in a community tank, unless it is bare bottom with no plants or decorations. If you want to breed discus, it is advisable to place them into their own tank no smaller than 20 gallons...a 29 gallon tall is ideal. Patience is the key word when breeding discus...it can take countless times for the pair to get it right and not eat their eggs or fry. As for plecos...no clue.
-Ryan