You could have carrot fly on your carrots, Bazman! Pull a couple up and have a look at them. If they have little holes and look as though something is burrowing through them, that's what it is. Other than that, it may just be lack of water or food. Look up carrot fly on the net, then you should get some pictures to compare with yours. Carrots need to be grown in a raised bed, or surrounded/covered with fleece/glass/clear plastic or some other protection to keep out the carrot fly, because they'll smell the carrots from miles away! Supposedly the flies can't fly more than a foot or so above the ground, so raised beds should be OK, but the ones that got to my carrots must have been acrobats, because the beds are about 18 inches high!! Sorry for all the bad news! Annie (Cumbria)