For the aquarium it is not necessary to imitate these values exactly, except for wildcaught animals that are recently imported. They are very fragile when in comes to water quality and the hardness of the water, captive bred fish are much more tolerant. I would recommend to try to keep the water conditions as follow:

Hardness: between 3 to 15° dGH
PH: Between 5.5 and 7
Temperature: around 30°C (86° F)

To lower the hardness of the water I would not recommend to use the supplements offered in petshops. The main reason for this is that the effect will not last very long because of the regular water changes. In my own tanks I use peat in my filter to lower the hardness. But there are other methods as well, which I will discuss at a later point.

Nitrate and nitrite levels
Besides the hardness of the water it is very important to keep the nitrate and nitrite levels within an acceptable range. I would not let the nitrate value come above 20 and the nitrite level is ideally not measurable. This is achievable by using a good filtering method, the right amount of fish and a regular change of 1/3 of the water. For my own tanks I change about 1/3 of the water two times a week. I use normal drinking water for this purpose, but I am lucky to live in an area where the water values are within an acceptable range.

Oxygen and CO2
When it comes to discus fish and temperature there is one last issue to mention. When you keep your fish at lower temperatures they become more susceptible to diseases. Because warmer water contains less oxygen it is important to have enough water surface movement. This way the water can better absorb the oxygen and get rid of waste products like CO2, 'real' waterplants like Vallisneria, and Ceratophyllum also have a positive effect on the oxygen/CO2 levels. If you like you can also use an Airstone, in combination with an air pump.