The easiest recommendation: get rid of the rapid fire turrets. They ware worse at everything than any other turret. I would replace them with a mix of rocket turrets and burst turrets. You are also nearing the point where you will see a lot more air than ground attacks. Keep an eye on it and decide if/when to move mortars over to burst/rockets.
In game name: Paper Tiger, officer in Hostile.Warfare
Line ID: paper-tiger