OK, shouldn't be an issue.
You do want to keep some space between all your antennas:
-Even with a 4 watt/12 watt CB, you can generate enough energy at the antenna to desensitize the receivers on the other radios. While it's not going to cause any damage, it might get annoying to have the receive audio drop out every time you transmit.
-Putting antennas too close together can change the radiation pattern. Again, probably not much of an issue for a CB.
But, just in case you ever decide to get your amateur radio license, GMRS, etc. making sure you give yourself about 19 inches between antennas would be a good choice.