Don't use potting soils in containers. This is great topsoil.

You can buy a potting mix made for acid loving plants and things will work out.

Only avoid regular potting mixes as they often have lime added to counteract the natural acidity of the peat.

Regardless of what you plant in you can maintain a healthy acid loving plant simply by watering with water mixed with fert for acid lovers or a little vinegar to lower the ph.

Evidently some may not even consider the above all that important in containers.

If you can't find a mix specially made for acidic plants, then mix in some sphagnum peat, which is what I have done for my blueberries, leucothoe, camellia, and other acid-lovers. You can mix in about 1/3 peat + 2/3 container mix or even up to 1/2 - 1/2. Fertilizing with Hollytone will help maintain the acidity of the long haul as it contains substances that will help reduce the pH. If you try a different fertilizer, make sure you read the ingredients because some ferts for acid-lovers do not alter pH.