Thanks for your reply. She isn't limping and seems totally fine, apart from the appearance of her paws. We did switch litter to a more fine and dusty litter. I will try to wash her paws and definitely take her to the vet if it doesn't wash away.
Noticed both my cats front paws have developed these growths on them. I can't even describe them. Has anyone seen anything like this before? She is a 1 year old domestic shorthair.