Few Questions

I was wondering if it makes a big deal if you use the same kinda light for growing flowering budding etc. I inherited a few plants and the set up and me being a lazy fuck up hasnt done anything more then water them and give them there proper lighting cycles. I have began to harvest them but I am not sure if they could get any bigger or not. All i really wanna know is if I will get some useable plant without all the extras of fancy different lights and nutrients and stuff like that? Oh and I have three of them and they are about 3 or 4 feet tall and I only have lighting on them from the top How much product do you think could reasonable come off of three plants this size.

HPS is good for flowering

hps for both or better Mh for veg hps for flower.