Azalea and Blueberries are acid loving plants. If the soil pH is too high, mineral deficiencies occur.
Hollytone is a very acidic fertilizer. There are generic versions of those such as
this. You do not want to water those types of plants with city or well water because it will raise the pH of the soil eventually. Distilled water, rain water, or tap water that is pH corrected is preferred. Any kind of manure also tends to raise the pH of the soil so those should be avoided if possible unless you want to continue correcting the soils pH.
You can probably use a general fertilzer such as Hi Yield Growers Special since most are somewhat acidic but you are better off with the specific fertilizer for Azalea and Blueberry bushes.
