I have two toenails growing at the same time on one toe and 3 toe nails growing at the same time on my other toe nail. I ve had this problem for 3 years now. I am a runner, but in all my years of running this just happened 3 years ago. It seems like that would be the reason, but Ive had no major injury that I am aware of. Ive had blisters under my nails but this is different. It seems to take a long time to grow out, now 7 months for the new nail to grow the old nail half way up. As soon as I have a regular toe nail, after waiting a year to grow the old one off, than it starts again, the cuticle has a split in the nail, and usually it takes about a month or two to see it growing out and then the old nail ontop goes yellow. The cycle begins again. I guess there is no cure, or stop running but it isn t causing any pain, it just looks wierd.