Yes.
What you have works, and works well, but it's simply too weak to really give you full blown grows. Read your own documentation. Your lights in flower mode are only strong enough to cover a 1.5 x 1.5 foot area at best. That's only 2.25 square feet. That's not really even enough to grow one single plant to its full potential.
A 600 watt hps light can do a 4 foot by 4 foot area with ease. That's 16 square feet. In the end, a single 600 watt HPS has more growth potential than all 4 of your 300 watt LED's combined. With ease.
Two of them and man, you'd SMOKE your current grow by a long, long ways.