I had the same thought, but I looked it up on the JD parts website and all three blades were the same part number. Good idea though.

Better measure them to be sure. I looked it up, also.
Did you have someone else sharpen them or did you do it yourself? If you had someone else do it, somebody else might be mowing with your blade.

I had someone else sharpen them, but I waited while they did it. I'm going to take them off and measure them. Thanks for the responses.

They may not be centered on the spindles (blade totally over the hole). If not, the blade will wobble and hit the others.

one of your deck bearings may be going bad i know this is unlikely cause its new but when they do blades tend to hit deck or eachother. dose it have a timing belt if so may need to be reajusted my john deere g15 has a timing belt and if it jumps out of time my blades hit good luck

Could also try offsetting the blades mine are 90° out of sink with the center blade. Seems to stay that way every time I clean the deck after mowing.