I think tbh, that Haewon is like me cursed and not able to handle hot weather well. This is the second time when she went to a hot country that she got ill and had to go to the hospital then deemed unfit to perform. But basically, she went to Spain, then on the day of the performance of Music Bank in Barcelona she felt unfit and ill to perform so they had her go to the local hospital and she didn't perform with the other members.
A little over a year ago the same thing happened, where she got ill while going to South America while it was also hot and humid and she also remained in the hotel after a local hospital checkup.