Jay insisted Sunghoon wore a particular shirt to his birthday party. Sunghoon didn't trust him, but it was his birthday so he gave in. Given Heeseung's reaction, Sunghoon thought he shouldn't have trusted Jay.
Heeseung keeps asking Sunghoon for him to use his magic to help him get a date with a witch. Sunghoon refuses because love cannot be forced and it's got nothing to do with his own feeling for Heeseung and his jealousy. Absolutely nothing to do with that.
Sunoo may have to intervene.