Maxi Amount of light per 8" plant in veg

Hi I have got 4 Monster crop clones in square 18 L buckets.
I have hung 1 light above the 4 plants (each bucket is around 12" x 12") so 4 feet square.
The ballast I am using 250w 400w 600w and 660 w.
The tallest plant is about 8 inches.
How many watts do you think I should have it on.?
Is 600 Watts too high for 4.?
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I have got a lot of cool lights and a couple of 1000-watt DE lights.
I plan on building 4 individual 1 square meter frames with a scrog net over I'm putting one plant in each corner of the 4 meter X 4 meter area.
How tall should the plant be before I put a 600-watt light above each individual 1 ?
I am going to build it up to three 600-watt lights above each one. Heat will not be a problem as they are cool lights and I have got 12 in intake and outtake and inline fans for the lights.
I do not want to shock them with too much life at once so somebody has told me to build the lights up over time but if I put a 600-watt light above each one now would that be too strong for them my.?
Thankspixs includedView attachment 5052665

Hi not quite sure what room size you’re looking at. People shoot for50 watts per square foot. So if you have a 4’c4’ tent or space that would equal 16 ft.². So a 600 watt you would just divide the 600 by 16=37.5. A 600 in there would work great. The problem with 50 watts per square foot is when we all used HPS and had to worry about heat. My old cab was 67watts/square feet, lots of heat issues. Hope this helps

I reread it, for 4 square feet you want 200 watts so the 250.

Light those up with a 660 all four

Edit: I reread OP, 4mx4m not 4ftx4ft, go hard with 1k above each plant or try heath robinson style with a bulb in each corner and one in the center and plants interspaced for maximum all round coverage. Unless you are running new full spectrum LED you likely won't be able to throw too much light at these plants which of you are just start them at maximum height and see how they deal with 100% power before easing it down, it's very easy to exceed the DLI maximum with new bar LED