I don't know if this is really an answer, but I've had a Coleman 6 person spa in service for about 25 years. Yes, 25 years! I have never had the same problems you are experiencing. We learned early on that any clothing (bathing suits etc) must be very clean and rinsed extremely well before going into the spa. Clothes cleaning detergents left in the fabrics release into the pool water and cause foam quickly. The clarifier is good at flocking these soaps, but they do tend to gum up the works quickly. We never lost a lot of pressure however, just had to clean the filter. We also made a habit of completely changing the water at least twice a year. After draining as much as we could via the drain hose, we used a wet vac to get as much out of any low spots. We then put in just enough water to cover the intake close to the bottom and jogged the pump to cycle clean water through the system and get the dirty water out. Again, drain and vacuum and repeat this process until the water looks clear. We do this with the filter out. This will clean out a lot of crap. About once a year just before we do a drain and complete cleaning, we treat the tub with anti-scale cleanser. This cleans the internal pipes of built up scale and solids. In your case, you may want to do this anti-scale treatment for a few days with the circulator on low and the filter out to purge the internal system. Then go ahead and change the water.
Another test you can do is to see how well the pump pushes water. When you have the small amount in the bottom, just above the intake, jets exposed, turn the jets to full, air off and see if the pump will shoot the water out of the jets with extreme force. Mine will shot water 20 feet away!!!! lol. If you don't have really good pressure, you may have a warn pump impeller. They can be damaged over time by chlorine based sanitizer, I never use chlorine, just bromine based shock etc.
The other item to check is if you have the right filter for your unit. Filters come in so many styles and densities. You may need to find one that allows better flow.
Assuming you find the root cause of your problem, good housekeeping, keeping as much contaminates as possible out of your tub will help. Very clean bathing suits or none at all,(yahoo) no body cosmetics such as body oils, moisturizers, perfumes etc. Keep chemical treatments to a minimum. Do a quick check weekly for PH, Total alkalinity, and bromine level. Adjust them sparingly so not to overdo any chemicals. Once you get everything under control, maintaining it is very easy and quick. Good Luck
No filter removes all contaminants. Carbon is great for improving the taste. The white ones remove large sediment. Activated alumina removes some fluoride among other things. Distilled water will be free of most things but volatile chemicals will make it through. UV light and micropores (ceramic and "nano tubes") will remove most virus bacteria protozoa and cysts. Uv light will kill most if not all of those little nasties if the flow is right.
So the first step would be to go get your unfiltered water tested. Then see what's in it that concerns you then figure out what you need to remove those contaminants. Your filter might not be designed to remove the stuff you have a problem with.
Best Answer
All of those are sediment (or possibly carbon) filters.
Three of them in a row is common for having increasing levels of filtration, eg: 20 micron -> 5 micron -> 1 micron. This captures bigger particles earlier, which increases the longevity and effectiveness of the smaller filters.
The pressure gauges give you an idea of which filters are getting clogged so you know what to replace.
There's no functional difference between opaque, translucent and clear filter housings -- it's just a different design. Arguably with the clear housings you can see how "dirty" the filter is, but practically speaking, it's much more useful to have pressure gauges. A filter that looks "dirty" may still be quite effective, while one that still looks fairly new may actually be clogged internally and need to be changed.