FFS...
Clean the children's bed sheets. Feed them healthy, nutritious food. Change their pajamas more than once in a while. Stop stressing them out with your own selfish ambitions. Keep their rooms as private spaces. Give them time off. Give them enough time in the school holidays to catch up with friends, homework and relaxation, rather than being dragged from pillar to post. Stop airing your dirty laundry, personal vendettas with estranged family members, or squabbles with online detractors. Be accountable for your actions, set a good example. Don't let them take the heat for your poor life choices. Don't let them watch unsuitable content on their devices. Don't expose them to the murky waters of social media accounts before they are old enough to consent. Don't vlog about their periods, fears, bathroom activities, insecurities, semi-dressed or near naked bodies....
After all that, only then can you be at loss as to why Issy is so ill... No parent of the year awards coming their way anytime soon. I know they're not the sharpest tools in the box, but none of the above is exactly rocket science!