Fine mesh resin is a chemically enhanced product made of calcite, alumina, and iron oxide. The 8% water softener resin has a much more refined and smaller surface area that can attract iron ions, which then attach to the resin surface. With larger surface areas, this resin can filter up to 10 ppm of iron from water, depending on the conditions.
If your system produces little or no water softening, you should check for retained hardness on the resin and use resin cleaners. The fine mesh resin can develop an "iron slime," which needs to be cleaned from time to time to allow maximum capacity.
Iron "Master" Filter System can remove iron from your water before using a softener. (Recommended) Resin cleaners, helps with iron slime sometimes developed by fine mesh resin. (Recommended)