Yeah, it may be two or more stages at the same time
if you end up with no filters and still no flow you can at least rule them out. This is what I expected to happen, but found it was one of my almost-new 5 microns plugged in just a day of use (incoming TDS only ~12ppm). I spent a lot of time doing other troubleshooting with the supplier as well. Good luck, I'm curious to hear what you find out,
Dan