Hi @mel1989 ,
Someone on here recommended Polybalm, or rather it was recommended by their consultant, for nails. It has been developed for people going through chemo to protect their nails. It is expensive but I thought it was worth a try - I ordered it off Amazon. I am only completed 3 chemo sessions so far but nails are doing ok. I use it at least twice a day. I have not tried painting them dark colours as I thought taking the polish off and on normally ruin my nails anyway and they would end up chipped.
I am also using nail oil. When it was sunny weather last week I put sun cream on them. Not sure if it makes a difference.
Good luck with your treatment. X