Discus are probably one of if not the most difficult freshwater fish to keep. Liveaquaria is well known for some inaccurate information such as minimum tank sizes and generally very poor quality of fish. Looking at the prices of discus you overpaid a considerable amount for discus. I paid 30-40$ for my juvies from Discus Hans.
I have never bought from liveaquaria I simply picking up on various threads I have read about them on other forums.
Because Discus are so sensitive you are looking for a very good bloodline. From big box stores you really have no idea what you're getting. Dedicated breeders will have strong bloodlines. They pay very close attention to what they cross.
I'm sorry to say, but did you research discus at all? Take this as a lesson learned. Before you buy any fish make sure you read, read, read, read, and read some more. The average lifespan of a discus is 10 years if kept properly. Pretty close to a dog or cat.
Let's get you on the right track now.
A stable PH is a good PH:
If you are doing water changes directly from the tap you should test both the Tap PH and check for a PH swing. After the 'gas off' your PH can change. If your Ph swing is big you need to age your water before doing the change. I bought a 40g trash can and use a heater with a powerhead in it. The movement will help gas off chlorine and stabilize the Ph. The heater allows to accurately match new water temp with tank temp
Discus are Warm Water Fish:
You're temperature should be a constant between 80-85F. I keep mine at 82F. New water should be nearly the same temperature as the tank temperature.
Discus are prone to Stress:
I couldn't tell from the picture but most agree you should paint the back and sides of the tank because Discus scare easy causing them to flee in a panic and collide with things potentially hurting them.
If any of this was redundant, I apologize I am just trying to inform not judge or be rude.
I work nights so I'm going to bed now, but if you have any questions send me a PM and I'll answer them when I get up. If I can't answer it myself I will find the answer.