Arms are big

Hello, so this has never happened to me before but basically i changed my skin and I always choose slim because I'm a girl and I think it looks better on minecraft girl skins and so I set the new skin as slim in body wise and my arms are really big. I don't know why but they are giant and definitely not slim and they just look really weird and I don't like it. They also have a black line on the ends of the arms. Please fix it, it looks really weird. This is very confusing for me as I've never had this issue and I don't know how to fix it. I tried switching between skins and logging into my minecraft account and out and it still doesn't work. I tried seeing if it was just the server I was on but in every server it is like that. So this is an edit but I was on hypixel and I asked in the chat if it was happening to anyone else and a girl said it is happening to her and her friends too, I have a screenshot that I will insert. Thanks.