Welcome to the community. That 1000 watt light isn’t that much wattage. Gotta love false advertising.
I have a 4x4 tent and it’s packed with 4 plants. Really packed. The more space you have the more the plant can grow under good lights. I wouldn’t put more than 3 or 4 plants in a 6x6.
I also want to know what light and or lights you are using.