Well, the plot could involve Robin's friends rallying around to take care of him. Maybe they bring him soup and keep him company while he's in bed recovering.
His friends like Batman and Nightwing could be main characters. Batman might use his detective skills to figure out what's wrong with Robin, and Nightwing could be there to offer emotional support.
Lissa would immediately spring into action. As a healer, she would be examining Robin, trying different spells and potions to make them better. She would be constantly by Robin's side, fussing over them and making sure they were taking proper rest.
In addition to his family and friends, the medical ninja in the village would be involved. They would be the ones to accurately diagnose Boruto's condition. Shizune, for example, could come and check on him, using her vast medical knowledge. And the other young medical ninjas might learn from this case, as Boruto's illness could be something new or unusual, so they would be eager to assist and gain experience while taking care of him.
First, you need to do some research on Robin's character in the Young Justice universe. Know his strengths, weaknesses, and relationships. Then, when writing about him being sick, describe his symptoms vividly. It could be something like a high fever that makes his vision blurry or a cough that won't go away.
In many Batman fanfictions where Robin gets sick, it often shows a different side of the dynamic duo. It could be a chance for Batman to show his more caring side. Maybe he'd take Robin to the Batcave's makeshift infirmary and look after him with great attention.
One common theme is the bond between Batman and Robin. When Robin is sick, it tests and strengthens their relationship. Batman's protective nature over Robin really shines through.
Seth could be the one to help her. As her brother, he would be very concerned and might use his own knowledge of Fablehaven and its secrets to try and find a cure. He could also enlist the help of some of the friendly magical creatures they've befriended, like the fairies or the satyrs.
His teammates, Sasuke and Sakura, would surely be involved. Sasuke, although he may not show it as much, still cares about Naruto. He would keep an eye on Naruto's condition, and if there was any sign of danger, he would be ready to protect him. Sakura would be more hands - on with the medical care, checking his temperature, giving him medicine, and making sure he rests properly.