I assume you still are balancing the water (ph, Alkalinity, etc) correct?
I have no experience with the Bullfrog @ease cartridges but I assume just like the inline ones made for Hot Spring/Caldera, Marquis, and Artesian, that you have adjustable settings. I have a Hot Spring SX using @ease. I have my mineral set to 6 and SmartChlor set to 2. Yes my hot tub is smaller (230 gallons) but it gets used every day by 1-3 people for a total of 30-60 minutes. Filtration on mine is set to run 2 hours twice daily. I shock weekly using SpaGuard Enhanced Shock, adjust pH and TA and add Natural Chemistry Cleanse Weekly. My first cartridge lasted 4 weeks and my second cartridge is going on week 6, but its almost empty. I've had no issues at all other than that the SmartChlor for some reason lowers pH and TA, which I already knew.
The SmartChlor cartridge life is variable and not guaranteed to be 4 weeks. The setting you choose, the size of your hot tub, the bather load and the amount of filtration will affect the lifespan. Low pH will also deplete the cartridge rapidly. I do firmly believe that the shock once a month claim by Frog is not sufficient, but YMMV.
Without knowing more information, I would have to attribute the water quality to either inadequate Frog settings, not shocking frequently enough, improper water chemistry or inadequate filtration. I have never used Baqua before but I think your experience should be considered the exception, not rule. Any hot tub that goes months without attention and still has clear water means you were either fortunate, had a really good ozone, or had low pH and the acidity of the water did not allow for anything to get funky.