If your soil is the slightest bit decent (moisture retentive, sufficient organic matter), there is no need to fertilize them at all. Contrary to common belief, fertilizing does not make plants grow faster - in fact, fertilizing when unnecessary can be counterproductive. Depending on what you have mulched with, an application of a moderate nitrogen organic product may help (most applicable to wood-based mulches like wood chips, shredded bark, etc.). Otherwise topdressing or mulching again in spring as new growth develops with compost will be sufficient and will help to retain moisture in the soil and supress weeds as the vinca spreads. I'd hesitate to use Miracle Gro for anything other than containerized plants - it adds nothing to the soil, if used frequently can lead to salts build-up, is expensive and too fast acting (a slow release organic formulation is always preferred).

FWIW, many folks find that vinca will spread much too aggressively and can rapidly become a nuisance plant, invading natural areas like woods, etc. I'd not encourage it to grow any faster than it is already inclined to do :-)