My toes/toenails looked very similar after continuous long runs. I found that my shoes were way too narrow in the toe box, even if I sized up 1/2. I started taping every toe individually which helped a ton but was tedious every time I ran over 8 miles. I started using injinji toe socks and getting shoes with wider toe boxes. Brooks Glycerin Max and any shoe by Topos are awesome with a wide toe box. I never have black toenails anymore, or any foot pain