I would consider a strong broad spectrum abx with gram negative coverage. That's basically doxy. Can use triple sulfa, furan2, and kanamycin. Just to mention a few.
I assume the red streaks are blood due to the attack from the flowerhorn. If that's the case then reduce stress, clean water and salt should help. Meaning not infectious.
Melafix and Pimafix really don't use as it doesn't do much. Some stress coat will help more IMO.
I bought Epsom salts online. But can get it locally from Walmart and other stores I believe, if you're in the US.