Hi Alan.
The coarse wheel shedding grit actually has an advantage. It stays sharper because when the grit comes off it exposes new sharper abrasive. It will cut cooler and faster while sharp but need some dressing to keep it flat and true. It has a softer bond, the "hold together" of the abrasive. Diamond dressers are not very expensive. If you get a lot harder wheel ( harder bond) it won't shed any grit and the grit glazes over, getting smoother. The smooth surface doesn't cut and it creates more heat, increasing the chance of blueing the edge, taking the heat treat from the metal. So use up the wheel while wearing a mask and eye protection. Then replace it with one with a slightly harder bond. The brand, if well known (Norton for eg), doesn't matter as long as the wheel has the grit size you want and the bond is correct. Your numbering code system on the wheels differs from ours so I can't tell you what to look for. If you go to an abrasive supplier to the machining industry they should be able to get you the proper wheels. Don't worry about the colour because different manufactures use their own even though the abrasive is the same.
Pete