half & half nails with no kidney disease?

Hello!

I've noticed about a month ago that I have what they call ""half and half" nails on all my fingers except my thumbs. My finger toes are all normal color (I'm caucasian). Then I went to see a doctor and he told me not to worry about my nails and said nails are not the only things to check and that other symptoms would come before. Anyhow, he decided to get me complete blood tests, wich they came all ok and normals. No signs of kidney disease, no liver disease or anything, everything is normal. The blood tests were:

sodium, potassium, glucose, creatinine, urea, calcium, total protein, albumin, AST, ALT, GGT, alkaline phosphatase, uric acid, total bilirubin, inorganic P04, cholesterol, triglycerides, HDL & LDL cholesterol, electrolytes, urine analysis, CBC with differential. All came back in the normals.

Now I don't know what to do, I keep reading on the internet that half & half nails is a sign of a kidney failure so I'm still a bit worried even if my doctor says not to worry and my blood tests say I'm perfectly healthy. What other reasons could cause this? Is it possible to have half & half nails when you are perfectly healthy? Can it simply be idiopathic? Should I continue to worry & seek or should I go see another doctor or even maybe a dermatologist?

Thank you for taking time to read this and answering me.