If I were you I would Def transplant the very small ones Into individual containers. 5 gallon absolute minimum.
The bigger ones are already in flower so not much to do other the let them Fininsh.
Also my advice is read everything you can get your hands on. Growweedeasy.com
Is a great place to start.
P.s. your friend doesn't look like he knows how to grow so I wouldn't take his advice.