i'm running 600 watts air cooled hood 4x4x7

First does girls need to be right under light? are can I space them out a little bit for example light in middle girls spaced out to edge of light it's four girls

A 600W is the correct size for a 4'x4' area.

However I would keep them close with the light as low as possible.
Until they grow to big to be that close to each other.
As they grow I would keep moving them outward as you raise the light up to accommodate for the height of the plants.
You always want to keep the light as close as you can without risk of burning the plants.

You want to keep the light at a height that maximizes its foot print. Closer is not always better. I keep my air cooled 600w about 18" from the tops.

MYOB said:

You want to keep the light at a height that maximizes its foot print. Closer is not always better. I keep my air cooled 600w about 18" from the tops.

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If you only have plants that cover a 2x2 area why would you "maximize the foot print" any bigger then a 2x2 area?
Is the tent or room you are growing in going to make bud along with the plants?
You raise the lights up till it fully covers the area your plants take up, You don't raise it to fill the whole area with light if its not full of plants.
I say again you want the light as close as you can get the lights without burning the plants.
I know of no bulb that is as bright as the sun, So it makes no sense to raise the light up more then you need to.
The higher you raise the light the less light gets to the plants.
18" is right about where I would keep the lights as well, how close did you think I ment?