Another Vet Visit

We just got back from vet because Minna was coughing badly this weekend. The vet said she has upper respiratory infection. The vet asked me if she had Feline Herpes Virus as a kitten but I didn't know since she was adopted. The vet took an x-ray of her lungs and told me it could be either asthma or simply lower respiratory infection but hard to tell at this point.

I just wonder what else I need to do so her respiratory symptoms will go away and she can be a healthy kitty, she already has premium high protein cat food, fresh filtered water, ventilated apartment, and clean litter box at all time, not to mention regular grooming sessions and vet visit...