#1- if possible, get each plant in its own pot. They will be fighting for space above and under the dirt. Dominant plants will choke out the small plants, but all will suffer.
Other than that, read everything on this site. Every sticky, post and whatever. Study a lot.
Dont over-fertilize, especially early on. Seems like a lot of new growers do this. Less is more and of you use strong fertilizers, build your way up to full strength.
Good luck. They look healthy.