I have a hexagonal hot tub of unknown age, model, brand. It's not very fancy and does not have many jets. I have replaced the filter in the past with a 50-square-foot FC2390. That filter fits, but it may not be the right filter. I have just discovered that filters of identical dimensions may have vastly different square footage. The spa jets are anemic. Could it be that we have too many square feet in our filter and I should get one with less square footage?