omg! It's not a healing potion. Requires Spectrum Potion. It should have been made in the first mission to lower Bernard's fever, so you already have learned it. If you can't find it even if you check the recipe note again, please contact me again.
Ah, I just checked the required materials in the save data,
the last one is just a normal health potion (:
I think it would have been fine if you had Bandages + AntiBreeding Ointment + Spectrum + HealhPotion in your inventory. After that, I think that if you kill time by repeating sleep and waking up until the morning for a few days, and talking with Tank, Scar will recover. I think it's a good idea to save once you have all the materials just in case.