My corn snakes tail looks like that... she is a 1.2m monster female and is a happy healthy snappy member of the family...
My snakes tail looks like that because she had weight issues... i.e. mummy over fed her
she went on a diet and is now in her proper weight range, but the tail is still the same.
if your snake is eating, pooping, shedding regularly and is showing no other signs of poor health... I wouldn't worry too much
Its just one of those things you keep an eye on and make sure it doesnt change...
Kind regards