Garlic

I have just harvested my garlic and have a good crop with large cloves. However, about half the bulbs aren't classically shaped - cloves held together in a bulb shape by a papery skin - but are very loosely held together with great gaps between the individual cloves. They were planted in October in heavy clay soil that had been worked for one previous season; they followed potatoes. I can't remember the variety. Anyone know why this has happened? It's of no great consequence as in fact the misshapen ones will be easier to peel!