He would probably get all flustered when he reads the article about you and Taemin. He, of course, trusts you fully but he still has to ask to make sure.
I feel like Jonghyun would just laugh it off. He trusts you so there is no need for him to worry about you and Key, he knows you guys are just friends.
When Key saw the article about you and Jonghyun he was a little worried. He was scared that he wasn't doing a good enough job as your boyfriend. You would have to reassure him that you love only him and that you are just friends with Jonghyun.
Minho would be fuming over the articles of you and Onew he wouldn't know what to do with himself. He would not take his anger out on you though. He would probably go ask Onew if there was anything going on between you and him.
Taemin would be like Jonghyun and would laugh it off. He wouldn't make a big deal about it but it would hurt him a little inside to know that the media would like to see you and Key together.