1. Your cartridges may be toast, or they may have been low grade to begin with, or . . . several other things. Post your EXACT pump / filter make / model PLUS your OTHER pool info (gallons, surface type, other equip: heater, SWCG, feeder, etc.)
Operate with the cartridges removed, and see if you have adequate circulation. Read the test kit page; get a local OTO or HTH 6-way; order a K-2006; test tonight with what you can find locally, and tell us the results. Tell us what the pool looks like and, if possible, send a picture to poolforum@gmail.com
2. Filters in general, do not do well with live algae. It sounds like you still have live algae: kill it! Is there thick sludge on the bottom? Are you on a tight budget, or is getting the pool cleaned up quickly a higher priority? (Best way to kill it depends on in asked for in #1 PLUS your priorities.)
3. Doubling up filters is NOT a good idea.
4. Most of the people who can give you accurate and reliable info -- the moderators and the PF Support Team -- can see your post right where it is, right now!
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