Propane Problems

Question

My grill uses propane bottles. It is new and worked fine through the first bottle. After I replaced the initial bottle, gas was slow coming out and would not get hot. Then I had no flame. Second bottle was definitely not empty. Bought another bottle (third) thinking I need a spare anyway. This bottle worked the first time. Now, it too is not getting enough gas. My suspicion is that I may have slightly damaged (stripped) ventilator gasket. What do you suggest?