What replacement grids have yall had the best luck with in the Pentair FNS Plus 60 sq ft DE filter? This is our first pool and already replaced a cracked manifold. Noticed a few of the grids had some broken spots in the inner plastic. Filter material is intact for now, but I would like to replace all at the same time and Amazon doesn't carry the Pentair brand of grids. I would like to use Amazon for the return policy if possible. I appreciate the feedback.