yea you have room, but take it from my experience, with doing only 4 different strains for my first grow it was a bitch and not possible for me to try and keep them all happy using just one "set" feed aka only mixing up 1 big bucket of nutes for them all ... each strain and even pheno's require different amounts of nutes so what may not be enough for one plant could kill another... ya follow me? now if u had a 10 pack of 1 strain id be more about saying go for it but if you want to do this right i would suggest just keeping with the 6 you have because they will be enough work as it is for your first grow.. but if your ambitious like i was go for it, worst case you lose a plant or 2 worth of yeild because you wont be able to give them each the attention they need... just my