Yeah, hard pics. I see what you are saying about the weak barbels and I can see no huge problems, like hemorrages, erosions, big inflammations, etc. but I cannot see the slight redness you refer to.
I hope you used a small or prophylactic dosage, as such dosages should not normally affect the biofilter. Without knowing more details, I'd say I would not use such a strong antibiotic. I'd use, if any at all, something like Melafix - a mild anticeptic (or a bit of salt). Some keepers report Melafix helps with cloudy eyes too (a potential benefit to you because your aro does not have it at the moment) - I admit I have no clue why Melafix would help the eye problems but several reports I've read on here cannot be denied, at least at their face value.
No, I didn't mean the tank mate aggression. I meant as your RTC was going through all those alarming symptoms, what his tank mates' behaviour was like? Normal or highy stressed too? Obviously if it was ammonia or any other water parameter far out of whack, as suggested above, all fish would be very uncomfortable and stressed in some way.
If they were not at all, then this points away from your water parameters and away from kicking-back your bio-filter and points to a bad reaction your RTC had to the med.