I would continue to think of them separately (a fertilizer + an amendment) instead of as a single item ("a fertilizer for acid loving plants"). Personally, I would not consider vinegar as something that makes the soil more fertile but rather as an amendment that makes the soil more acidic.

By the way, it is quite late to be fertilizing in Zone 5. Fertilizers, especially those high in nitrogen (Miracid) can keep the plants in 'growth' mode at a time when they should be going dormant. Early frosts could suddenly hit and kill tender new growth. Most potting medium already contains those round fertilizer pellets so I would consider fertilizing beginning in Spring 2010.

What kind of plant is this 'miracle plant', kurite? Sounds like it not an Azalea or rhododendron. Something else?

Miracid is a heavily advertised but not terribly good fertilizer for acid soil plants - its effects are very short lived. Hollytone is a much better choice. There is also an important difference between a fertilizer which makes its nutrients available at low soil pH and a soil which is acid. Depending on the natural pH, soil can be acidified by adding quantities of organic matter with an acid reaction - partially decomposed bark is my first choice although many people use peat moss. Once the soil is acidified a fertilizer such as Hollytone is highly effective. Forget the vinegar.

Sorry i left out some info. Im growing it as a houseplant. And i wanted hollytone but i am suppose to use a liquid fertilizer.

I woud repot florist azaleas in a different pot from the one that they come in and I would also keep a close watch on soil moisture because azaleas do not do well indoors. Maybe it is the lack of humidity or high indoor temps. If the potting medium is something special then I would repot when the company recommends that you replace the potting medium. At some point, I would switch to Holly Tone, say when they recommend repotting or replacing the potting soil. The only thing that I have been able to grow well inside are tropicals and (for only 1.5 years only) and a named gardenia variety.

Here is a link that might be useful: UMN's Care of Greenhouse Azaleas

"Miracle plant" is not an azalea :-) It is a tropical plant, Synsepalum dulcificum, that requires indoor care in colder climates and acidic growing conditions. For a houseplant, Miracid (or MiracleGro for Acid Lovers) is a perfectly reasonable fertilizer and is recommended in this link. You do NOT want to add vinegar to water and use regular MG - it is NOT the same :-) Miracid will supply specific nutrients that acid lovers require that may be bound in less than ideal soils or missing in plain MG.

Organic fertilizers tend to be rather ineffective for houseplants or in container growing situations - this concept has been explained to the OP in detail in various other forums - so it is far more efficient to use water soluble synthetics to supply necessary nutrients. Hollytone won't work.

Here is a link that might be useful: Miracle fruit plant