This will be my 4th season using 15 gallon containers for my tomatoes. I didn't notice any production decline last year, but I expect that the soils have broken down over the seasons and I want to keep the roots breathing. I would prefer to salvage what I have instead of refilling all 60 containers. The original mix was a blend of mostly Pro-Mix, Sta Green and Miracle grow. Would blending in more perlite and or pine bark be an okay solution or is there something better?