I wish i could afford running the lights 20/4. Unfortunatly this is my first grow and i spent way to much on my setup. Next batch of seeds I ordered is fem white widow.
Well in that case let me give you an advice then , next time dont go Auto's , but this time you are worried about the costs , do one thing. you have 2x400W Bulbs right ? .. shut on blub off and go 20/4 .. it will cost you less than the 2x400W running 12 hours , and i bet wit will give you better yeild , because i dont belive with 2 plants that size and that configuration with 2 separeted bulbs you aren't wasting light . cause i bet you are.. alot.
2nd thing and also very important, when it comes to auto LST is pretty much the only thing you can without compromising yeild , push down this top colas with some "ropes" slowly so you dont shake it too much. and spread your plants like a flat screen , use your imagination just dont let them grow as a pine tree , sun light as no losses over distance a plant can grow as she pleases in nature when it cames to indoor thats a totally diferent scenario you want all the
fan leaves(plant solar panels) to be as close as they can feeding on the light because there is a GREAT lost over distance.
And then put the two of them under 1 HPS for 20/4 , you will have less cost in electricity and i promise you will have better yeild. probably almost double.
I would say about almost 100 G a plant if everything goes well .. because like that i belive you will get 50G dried from each plant .. if soo.
PS: i also just didn't understand from your post if you have 1 MH and 1 HPS or 2 MH ? your weren't clear when you said i bought another bulb ?