How can I keep collections separate in a clothing store?

[Justin_bayes]

So I'm having a bit of an issue with keeping collections separate, I have a clothing store and I have catagories - sweater, t-shirt, joggers and leggings

I inputted the correct collection with the sweatshirts 

I move on to changing the collection on leggings catagory to leggings, once that change has been made it changes the collection on sweatshirts to leggings