http://www.baldwinfilter.com/literat...9;s/89-5R3.pdf
The gist of it is that there are different test methods used to rate the filter media and clearly your two filters did not use the same method. Look for a different sediment filter cartridge.
Since you are pulling water from the lake, rig up a back flush to occasionally blow the crud back out into the lake and prolong the life of the cartridges. With a backflush setup, you can only use one filter though, not two in series. You could also rig up a second filter in parallel with valves that let you switch from one filter to the other instantly that you always have one clean filter ready to go and have no urgency swapping the element in the clogged filter.