It's likely your a victim of misleading naming/branding.
You need at least 30w per sq ft. That's ACTUAL watts from the wall.. just because it says "1500w" somewhere on the packaging, doesnt mean the actual draw is 1500 watts. These knock off brands do that to mislead people into buying a cheaper product. They'll sell a 200w light, and label it "1500w equivalent". Shady stuff
A single 600w HLG has a 5x5 flower footprint.. so even with a product from a well known and trusted source of quality LEDs, your not getting enough power to cover a 7x7 (49sq ft) area. You'll either need 3+ more of those lights you bought, to properly light your grow space.