I notice that sometimes a few of my crops grow faster/later than the others that were planted at the same time. This usually happens with potatoes - I plant 24 and one or two still have another day to go when the others are being harvested. I noticed this happened recently in my tomatoes too. I usually don't use fertilizer (only if it's the last few days of a month), and I'm sure that the areas where plants grow a little faster/slower aren't fertilized at all. Does anyone know why this happens?