8 month old kittens hate littermate after illness?

I have five 8 month old kitties that were born to a stray mommy cat. One of the kittens developed horrible conjunctivitis from having FHV (2 other kits have had flare ups too), and she ended up with an ulcer on her eye. She had been isolated from the others for about 4 weeks. Now that she is better, I've been letting her out of isolation. She has no problem with my other cats (the non-littermates) and they have no problem with her. Her 4 siblings, on the other hand, HATE her. They hiss and growl and one even stalks her and tries to start a fight. Prior to her getting sick, they all were very tightly bonded. Never a problem. Now, they suddenly hate her. I don't feel that it is because they think she's a stranger (after having been isolated for so long) because I just moved back in with my mother and they all get along fabulously with the cats they'd never met before here. They didn't hesitate to go up to them and start cuddling and grooming. All of my and my mom's cats are very well rounded and used to newbies because we rescue and foster all the time.
So, I just wanted to see if anyone has any ideas about why these babies are acting this way towards their sister? It's so strange. Like they know she's the weak one or maybe she smells sick? She's still getting eyedrops 3 times a day and is not 100% recovered, but she's no longer contagious and healing will take several weeks or longer according to doctor.
She's still her loving little self and wants to cuddle up with them, but they will not allow it. Passionate, passionate hatred! Thoughts?