The kits are the same, except the "c" version has larger amounts of reagents in it.

Keeping your chlorine above 12 ppm can take LOTS more than 4 gallons. You just have to keep testing and adding more until the pool clears up and the foam dissipates. The "swamp treatment" likely has created even more of a chlorine demand, and if your CYA was high at the end of last season, it also can breakdown over the winter into ammonia and create huge chlorine demands. THey can be overcome, but you need to be diligent about it.

Janet