When bass are just slapping your bait, short striking, or following but not hitting, they're telling you something. You're close, but something isn't quite right. Almost without fail, it's color in these instances.
Change the blade color, skirt color, or trailer color - one at a time - until you find out what it is. Sometimes it takes just a subtle change. Remember, you're almost there, so don't make huge changes.
Hope that helps!