Azaleas don't need acidic-tending fertilizer per se, but they do need a pretty acidic growing medium in terms of pH. The acidic fertilizers help get to that lower pH.

In order to help your azaleas thrive, you have to take measures to keep the container soil pH down lower than 5.5. If you can afford it, I'd water them with distilled water (or rain water is you live in a rainy area and can collect) and a weak solution of Dyna-Gro Foliage-Pro. If you need to use tap water, add vinegar until the water pH is under 5.5. Then add your liquid fertilizer.

You should go to your county's website and find out your water source's characteristics from their annual report. Look for pH and alkalinity. If they are high, you really can't water your azaleas with that tap without modifying the water first.