Took the polish off and my toenails underneath are yellow

I have had a dark red on my toes on and off since spring, and I took it all off last night to give them a break. Every nail underneath is yellow. Not a bit dull, properly yellow, and the big toes are the worst.

I had not used a base coat because I did not know that was a real requirement rather than a way of selling you another bottle. So I assume this is staining and it is my own fault.

How long does it take to go? Is there anything that speeds it up, and is there any point buffing them, or does that just make them thinner? I have sandals on all week so I am slightly regretting the timing.