switchable ballasts r the way to go. For veging u need MH bulbs and for flowering u need HPS. These arent required thow. U can use wat ever u have but if u dont get the right stuff u may aend up kiking ur self in the ass later. Just get a switchable and for 4 plants u only need one. Ur best bet is to get a switchable 600 watt ballast that is also dimmable wich means u could use a 600 or a 400 watt bulb with the same ballast. B sure to get a digital ballast to man. Magnetic ballasts r loud and dont put out as much power ad electronic ballast. Its a great advantage and if u buy a good one from hydrofarm like a lumatek it will cost u about 250 bucks. Good price and comes with a 5 year warranty. If u buy cheap like I did when I started growing ul end up geting prety frustrated lolz. Ul save money and stress buy spending a lil more at first. If u dont it will end up costing u more in the long run. Hope this helps!
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