I agree that this all started when Hwayoung tweeted something, then her sister tweeted, then her rap couch tweeted and she still hasn't stop tweeting even though news of the members bashing her are already out. Her tweets, for me, is more like accumulating fans by tweeting pitiful statements.
At first read. I would say that EJ and HYM tweets are not insulting tweets and if it were for Hwayoung (which i doubt it is, because I don't think the girls will risk their image just to bash her), I think it was said nicely, but I've got to say that Jiyeon saying "I applaud you, acting genius." was a bit harsh if it were really true that the tweets were for Hwayoung
After knowing that Boram unfollowed Hwayoung, and Hwayoung deleting pictures of her with members, thats when things get serious. I really don't know what's happening inside the group but i do think there is already a problem inside the group, remember that in the 5 girl's tweets they seem to agree with each other, meaning they all feel the same way, so maybe Hwayoung really does or did something that made the other 5 members feel that way about her.