removing a plant from bad soil

What would be the best way of removing the plant and transplanting it in new soil.. should I unpot it and was all the soil off the roots and put it in new fresh dirt or just transplant as usual? I reused my soil and my plants are not growing but look healthy... I know it's the soil..

I wouldn't wash them. Plant them with whatever bit of soil sticks to the roots, they will find their way to the new food. If not much old soil sticks, you're still ok, just be gentle and don't leave the roots exposed to the air too long. A few minutes is certainly no problem.