ok say i have 2 600w hps lights and 20 plants to go with them ,would i get a better yeild if i used 3 or even 4 lights ,thats assumeing everything else is in order (nutes/temp/ph/humitity/ect/
Two 600 watters should work for 20 plants. You won't have seven feet plants, but if you kept them to four feet or less that would work.