I am assuming in my reply that we are talking about a wild European hedgehog who has access to natural food as well.
Yes, stop feeding the mealworms. Do it gradually if the hog goes on strike and refuses to eat. Also give the digestive biscuits a miss. Not good for the teeth apart from anything else. The hogs don’t need any extra treats, what we give them is the extra treat and you’re better off sticking to the cat food. Make sure that there is water available 24 hours a day, every day, all year round.
Is it the actual skin which is white or the spines. If it’s the spines, it may be that someone has artificially marked the hog. If it’s the skin, it might be a good idea to ring your local carer/rehabilitator/wildlife hospital and explain it more precisely to them and take their advice. You can find the number of your nearest ones by contacting BHPS on 01584 890801.
Good luck. I hope the hog continues to do well.