Toenail Stain?

Its just from having polish on constantly. Its not the color. When you polish, no air or sunlight gets to the nail. There is nothing wrong with the nail, just discolored.
AND, it looks thicker to you because it probably is...when you keep polish on constantly, the nail doesnt "shed", as it were.
The solve? Dont paint your nails for sometime, get them out in the open and have them filed a bit.
Natural color should come back...(unless, of course, you start painting them again)

I second the base coat suggestion. Maybe they didn't use enough, or you need a better one for some of the brighter or darker colors.

Make sure you put a base coat on, which should keep the color from staining your nails.

I don't know if this will help you or not, but I used to paint my toe nails all the time. I am now in my 40's and just last year I took nail polish off after it had been on during the summer (mine lasts a long time) and my toe nails seemed to be "stained" like you had indicated. So I left the nail polish off and it eventually went away. I don't know why that is, but I don't use nail polish (even clear) on my toe nails anymore and I don't have the problem anymore. I hope this helps.

Usually, darker nail polishes like red or bright pink will leave a yellowish residue upon removal, unlike a soft pink or white nail polish. The staining usually will disappear with time, but I am surprised that the doctor did not know this.

same thing happened to me and has been that way for months .. it is what it is, at least from my experience.

Yes it is normal if you use polish all the time. It's because your nails can't breath under the constant use of polish. Your finger nails will do it too. It will grow out of the nail as it grows and it won't harm you or using polish in any way.

S.