When you say yellows, is that yellow perch. Maybe your crappie have gone to deaper water than what you were fishing. I don't know nothing about your fishing area but I would look in deeper water than you were trolling in. Try locating your fish before wasting all your time trolling. Here in Idaho I always locate my quarry before I start fishing. They may be in 30ft. of water or 70ft. of water. There depth dictates on how I present my offering to them. If I find fish at fifteen foot I use a slip bobber setup. If I find fish at 60ft, I vertical jig for them. I anchor over the fish. Good luck next time out. Going crappie fishing tomorrow. Air tempature is in the upper 30tys. Afternoon in the upper 40tys.