6 weeks is awhile....even tho the flow is still good. If you have been running your pump frequently, had a lot of debris/pollen/dust, etc., or vacumed, it can become pretty dirty. We have a cartridge filter, I would say we hose it off once a month (or more if the heater doesn't kick on it's usually from a dirty filter).
I would say, for fun, LOL, hose it off, and then make a note of your clean filter pressure....
I'm not sure if we have the same one, but I also have a Proline filter.
First thing to do after shutting of the pump, is to close your valves at the skimmer and return. That way you will not drain the pool.
Second, there is a plug at the bottom of the filter that needs to be removed. This will allow the water to drain out of the filter and pump.
There is a black ring around the middle of the filter that has 2 yellow handles on the underside. One of the handles will push up. Push it up while turning the ring. It may be difficult. I usually have to tap it with a wrench to get it to start turning.
Once you unscrew the ring, you will be able to grab the top by the handle and take it off.
Unscrew the knob on top of the cartridge and slide the cartridge off of the plastic thing (sorry, i don't know what it's called) in the center of the filter and hose it down.
Once you reassemble the filter, make sure the plug is back in the bottom. Open your return and skimmer valves and partially unscrew the little cap on top of the filter.
Turn the pump on and when water starts to come out of the top of the fllter, screw the cap back down and you are done.