You didn't say whether or not you had humidity domes over them and that will affect what you do somewhat. I have trouble with humidity domes, because mine tend to want to wilt when I take it off. I have to baby them and introduce more holes to allow more air flow and get them used to it gradually, though in SC the humidity is high enough to feel like you're swimming some days.
If not, then I'd leave them in their pot for as long as you can stand it or until they show negative results of it. You can expect some root die back regardless of how gentle you are, because you're disturbing them and changing media. Even if it's the same media, it's going to have more and possibly different nutrients. If they're happy the way they are, then leave them there to get the best root system you can. The stronger the root system, the less die back will affect them. One thing you could do is start teaching them to be drought tolerant. I'm sure you watered them to keep the soil moist when they were gaining roots. You can let them dry out slightly to inclement them to this as once they're established, you probably won't be watering them as frequently.
If and when you do repot them, definitely don't pull them out by the stem as the roots will be anchored as well as tangled with the roots of the other plants in the pot. Weave your fingers in between the bases, as close to the dirt as possible, tilt it upside down or to the side and gently squeeze the pot to get the dirt to release from the pot. Then let the whole mass slide out. You should have your other pots or ground spots prepped already with holes dug, potting soil amended in it and more dirt ready to pack them in. You want to do it as swiftly as possible to avoid drying out or stressing the roots.
Take the mass of dirt and plants and see if a gentle squeeze here and there will cause them to break apart into individual plants. Chances are that some roots will be tangled. Just break or cut them away. Do this as little as possible, but you can do more damage trying to save every root, than to sacrifice a small portion and get it done quickly.
When you have them separated, either get them in the ground or put them in their pots. Either way, water them thoroughly to give the plant a boost and to settle the dirt. If they're potted, then put them in a shadier spot for a week and then move them back in full sun. If you are putting them in the ground, you should add some potting soil, but mix it in with your regular dirt about 50/50 min. I live in an area with lots of clay and one thing that's been known to happen is a plant does poorly because A, the difference in the potting soil and the clay are too great and the roots don't want to leave the hole and spread, and B, the clay is so slick and packed that if you don't scrape the side, they just spin around in the hole instead of spreading out. Good luck with your plants.
