Miracid very temporarily lowers soil pH. It's main value, however, is that the contents are in a chemical form that makes them available to plants growing in acidic soil.

Spreading sulfur or any other acidifying amendment around without doing a pH test first is never a good idea. Without knowing whether its needed or how much to add if it is, you're in danger of doing harm rather than helping.

Also, a water soluable fertilizer like Miracid acts very quickly and is very expensive per volume. Blueberries and azaleas will be much happier with a slow acting fertilizer like Hollytone.

Before doing anything, though, test or have tested the soil and determine why things are not doing well.

If the hydranga flowers were pink, then increasing the acidity may make them turn blue. The blue in hydrangeas requires both acidity and aluminum. However aluminum eventually kills rhododendrons and azaleas. So it is never a good idea to mix rhododendrons and hydrangeas if you want blue hydrangeas.

You did the best thing you could to increase the acidity. As mainegrower mentions, increasing the acidity may not be a good thing. Just as hydrangeas have pink flowers when the acidity is low, rhododendrons have chlorotic leaves when the acidity is too low. This means that the leaves are yellowish between green veins. If they are uniformly yellow, then there is a nitrogen deficiency.

You picked up on the problem with water soluable Miracid. It forms a liquid with a very high nitrogen content and does little for the acidity of the soil. It is acidic by itself do to the pH of its ingredients, but being water soluable, it doesn't last long. And nitrogen causes tender green growth which freezes in the winter and inhibits flower bud productions.

Sulfur is slow acting, but is extremely effective in decreasing the pH (increasing the acidity). The levels needed are on the order of a tablespoon per square foot depending on the situation. If the plants are not chlorotic, then sulfur won't do any good. Sometimes chlorosis is caused by too much acidity. The is seldom the case but has occurred in the Pacific Northwest where some places have very acidic soil.

HollyTone is a good product with sulfur and moderate nitrogen levels. There is a dry Whitney Farms or Miracle Grow Shake'N Feed Rhododendron and Azalea product for azaleas and rhododendrons that isn't nearly as bad as Miracid.

With any fertilizer only use at half the recommended rate and only apply once each year at most and apply during bloom season, never in summer or later.

Here is a link that might be useful: How to care for rhododendrons and azaleas.

Thanks for the feedback, I really appreciate it. I've had soil tested in the past. If my hydrangea and azalea, which are close to one another, don't look better this year, I will get it tested. I hope I didn't apply too much Espoma Soil Acidifier. I followed the instructions on the bag, but it was significantly more than 1 tablespoon per square foot. Oh well, I usually allow myself one episode of risky mad-scientist behavior per year. I know my hydrangea and azalea were pitiful last year. The hydrangea was bigger the year before that, because the stalks that I pruned off last spring were twice the size as what grew last year. I don't remember the color of the flowers. This is our 2nd year in our house, and this is all fairly new to me, as I've not had plants like this to maintain before. Thanks again.

I just checked and Espoma Soil Acidifier is Gypsum and Sulfur. It should do a good job. It is only 30% sulfur, so it would take more. Wait before doing anything else. I doubt you could do any harm unless the soil was already too acidic. Hydrangeas tolerate very moist soils. Azaleas need very well drained soils. So it may not be too good of an idea to plant them together. They are like acidic soil, but azaleas can't tolerate too much aluminum and blue hydrangeas need some aluminum.