Raised brown spots on garlic
The brown spots can be a bruise from handling or a bruise caused by heavy soil.  We learned the hard way to avoid planting in heavy clay.  Loads of brown spots from cloves trying to swell against hard soil, or a rock or buried root etc. The bacteria get into the bruised clove and quickly discolour it. 

We added lots of compost and tried to make our garlic patch soil the lightest, fluffiest texture possible.  The softest soil produced the cleanest bulbs.  Also far less bruising from harvesting since they pull so easily out of the ground.