One of two possible problems that I can think of: wrong sized blades or bent/shifted spindles. These blades should spin freely and never make contact if the spindles are properly centered in the deck openings and they are perfectly vertical; that is so longs as you have the proper sized blades. Whatever it is that bent your blade likely shifted or moved something which has now created this new problem. I would suggest completely removing the deck, cleaning the area around the spindles and checking to make sure that you do not have any damage to the spindles, shafts or holes where the spindles mount. I am not sure of the strength of the deck upper, but a substantial enough of a hit could have bent the top causing the spindle to no longer sit properly.