If you planted them correctly, all you need to add is water for the first year. If you planted them incorrectly, you will need to fix this.
Correct planting occurs when you mix compost, slow release fertilizer, and other non-chemical organic amendments to the soil you are planting in. Combine 1/3 compost, the fertilizer and organics and 2/3 native soil together in a wheelbarrow next to the hole you are digging for the plant. Put the plant in the hole and back fill the plant. The hole should be twice as wide as the plant's rootball, and you will only need 1/2 of the soil from the hole. After backfilling, use any ammended soil for your other plants. Water the plants and then apply a water-based root stimulator.
Incorrect planting is when you dig a hole the size of the rootball and place the plant in the hole, then water it and think you're done. The plant will look good for maybe 3 months then start to look bad.
Improper planting is the #1 cause of plant returns due to the common complaint, "you sold me a bad plant".
If your plants are already planted, you can either dig them up and plant them correctly. Or you can waste money on water soluble fertilizers that only have a 10% absorption rate. Your last option is to dig holes at a 45 degree angle, two per plant, and input your slow release fertilizer and organics, just under the rootball. Coincidently, this is what you do in springtime for the first 2 years. After that, you will need to get a tree and shrub or flower fertilizer for top feeding.
Miracle gro is cheap because you have to keep applying it once every week, or month. The easiest and cheapest way to feed your plants is to go to the plant nursery, get the slow release fertilizers and composts (make sure it has mycorrhizae in it, that's a beneficial fungus that assists the roots), and use them as directed by the nursery professionals.