What can be causing my toenails to split?

[Doonhamer]

both big toe and 2 nails on left foot and one on right foot have split. About halfway down the nail bed, and I am having to keep them covered up with plasters to stop them catching on socks

Fungal infection is the most likely cause. Treat with OTC Amorolfine (Curanail) or go see a private podiatrist for their opinion?

I thought there would have been visible signs of a fungal infection but there's not, just a horizontal split on the nail