How long have you had the tank?
Did you test the water before or after the massive water change? Or both? If before what was the result? No point testing after such a large water change, you are only going to see the parameters for tap water. Let the tank run for 24 and test. Post actual numbers, not just "no problem".
Why did you have to lower the pH? Fish can adapt to a range of pH. Its more important to have a steady pH than trying to get to what you think is the ideal. Trying to alter pH just causes fluctuations which is stressful to fish. If the natural pH of your tank is between say 6.5 and 7.8 thats fine.
Leaving the light on 24/7 isnt a good idea. Fish need a period of darkness to simulate natural day and night patterns. 12 hours on at the most and even that could cause algae growth. 6 to 8 hours on is what people commonly arrive at to keep algae at a manageable level. Your water does look a little green, but that could be the colour of the walls through the water.
Tip on aquascaping. Get a black background for the tank. It will hide all that equipment down the back of the tank and cause all the things in the tank you want to see to really pop out. It will also give your fish some added security and reduce stress.