From the Rock Spray Nursery catalog:
Each spring use an fertilizer for acid loving plants....They do not recommend Miracid....use a slow release granular fertilizer....heather does not survive in a soil that is high in nitrogen...use a 5-10-5 formula appropriate for other acid loving plants.

Jim

Follow JimÂs advice to the letter. Calluna grow naturally in sandy conditions. Sand is low in nitrogen (and not high in anything else, either). Adding just a bit of compost at planting time is okay, but that's all they'll need or want. Most heaths and heathers are s-l-o-w growers.

Miracid and the like are great for annualsÂespecially for those in pots, but should never be fed to perennials. Adding fast-acting fertilizers will result in plants' absolute dependence on chemical fertilization.

I planted mine with a bit of Espoma Plant Tone...don't think I will give them anything further.

I'm new to heather growing, but I've had good results mixing leaf mold into the soil along with Dr. Earths starter fertilizer. I use that for everything I plant and have had good results with it. I don't know if they mention it on their website, but you can learn what they do in their mixes.

Here is a link that might be useful: Doctor Earth Fertilizers