BradZA

Another parallel string should do the trick. The inverter will only draw what it requires, even if you have 6000Wp worth of panels, the inverter will only draw 3000W from the panels.
When adding panels with a total Wp more than what your inverter can utilise you just have to ensure that the Max Voc of your panels never go above the Max Vin on the inverter.  Since you are running 3 parallel strings already and just adds another parallel string of the same kind of panels that should not be a problem, because you should have checked the Max V on your current set-up already.

Thanks for all the assistance. I agree that my panel size is to small and I don't have enough to keep the system going.    What my plan is to do. Im going to buy another 2x300W panels and setup 2 strings of 3x300W panels to increase my voltage through my MPPT. In another month or so, I will purchase another 3x300W, so then ill have 9x300W panels with 3 strings and look into Viltron BMV 702 monitor.
This is my first time using a mppt controller as I have always used the standard for my small systems on my towers.
I will post an update this weekend or next week to the improvements of adding and changing my panel strings.