Before transplanting, you want to wait til they are ALMOST root bound. I say almost because you don't want them to be actually root bound. (this stresses the plant). When there is very prolific root growth, go without watering for at least 4 or 5 days (enough that you can lift the entire soil plug out of the pot without it falling apart. Mix up a spray bottle with some B1 root master and spray the outside of the plug until wet. Dig your hole in the new soil that will house your plug. Spray the inside until saturated with the B1 solution. Wait until it absorbs and turns from almost mud to s regular looking soil. Transplant. If you have a hot house cover, now is not a bad time to use it!!, Make sure your mediums are relatively close in temperature and moisture. No root shock and the plants wont hurt. They won't veg as much for the first week or week and half because the B1 will make it focus on the root growth, but don't get worried. After that first critical week, your good to go. Word to the wise, DONT OVERDOSE YOUR B1!!!! You will nute lock that plant!, I use the root master B1, just follow the directions, mix it proper.
Grow Strong