Yes, 5sandown is right, it has been discovered over the last few years that mealworms are bad for hedgehogs, due to the inbalance of phosphorous to calcium. There is too much phosphorous in relation to calcium, which causes calcium to be leached from the bones of the hogs leading to weak and easily broken bones. It’s particularly dangerous for hoglets which, when fed on mealworms grow in a deformed manner. This is added to the problem that some hogs become addicted to mealworms and refuse to eat anything else, which can be life threatening, even once they are taken into care.
What you need to do is offer them some other food, but without the alternative of mealworms. They may ‘go on strike’ for a few days and refuse to eat it, but if they are hungry will eat the alternative. You must stick to it and not give in. It is better not to feed them at all than to feed them mealworms, because if they fill up on mealworms, they may not eat as much other more nutritious, and particularly wild, food. But make sure you always provide a supply of water all day every day.
There are various hog foods around, which cats aren’t supposed to like, but alternatively you could try to make a cat proof feeding station and feed cat food. There is some information here: https://www.hedgehogstreet.org/help-hedgehogs/feed-hedgehogs/ But also lots of ideas in the Gallery (accessed via the home page).