Freddie's Sick

Freddie is part of a two kitten litter, Freddie and Karl. Both male, born middle of march 2024. I got them from the same friend who gave me one of my other cats, K'leah, female, 2.5 years old. All 3 are full blood siblings. K'leah is diagnosed with asthma, and Karl has the same symptoms but no official diagnosis yet. I also have Kenny, who is 15.5 years old, and has no relation to them, he's a huge cat and a total sweetie. Kinda a scardy cat. Freddie has been sick for the last 2 weeks, and was sick with similar symptoms recently as well. It seemed to go away for a short while, maybe a month, and then immediately come back but twice as bad this time. First time he was sick he had a fever and his inner eyelid was part way shut. He got a full course of antibiotics over one week, then the fever went away but the eye stayed part shut for nearly 3 weeks even with two different drops. Second time he got sick he again had a fever, and his OTHER eye had the same symptoms as the first time. We used the antibiotics, but at the one week check in he still had a fever. The Vet suspects feline herpes, no other cats in the house seem affected and they're all inside cats (except for K'leah who gets taken on supervised walks) (we live in the hood) Yesterday, his two week course of antibiotics was over, and he seemed 100% good in the morning, but then in the afternoon he woke up from a nap, jumped off the top of the cat tower, and attacked the 15.5 year old sweet heart kitty. His littermate came tearing in the room, hearing his brother screaming, and joined the fight, this happened right next to me while I was working on the computer, so I immediately stepped in and split everybody up, it was going on for a maximum of 5 seconds, but Freddie ran off and hid in a corner, still Yowling, even though there was nobody around him. I checked his temperature at this time, and an hour after, and both times he had a fever after having having no fever that morning. That is one thing i've noticed about when he gets sick, he'll be great in the morning and starting at roughly noon he starts to crash, then early afternoon he crashes hard for the rest of the night. I can't find anything on these symptoms online, and he's going back to the vet first thing in the morning, we have an appointment, (they were booked today) Thought I'd post here as a last ditch "ask the internet" type deal Please, if anyone has any ideas, my ears are open