For me the nail changes on my toes happened late. I would say 2 years into dx and this last year it really has become bad. Right now they are so gross and hard to cut. Its been about 4.5 years with the condition.
As for what helps heal. I am not sure but I think if the RSD pain and condition gets to a better place with treatments then the nail issue will also improve. Like for ex when people do ketamine and the sores start going away. It may not be ketamine but another treatment it was just an ex I was using.
I don't take biotin but do take supplements. I think vitamin c and also omega 3 also help in healing. I also thought I read that lack of calcium can impact nails etc. I have osetoporsis so I take calcium with d anyhow.