Hi bluefire
No, I don't think it was the plants. Fish catch bacterial infections from bacteria that are commonly found in tanks, but only when something has caused them to have a lowered immune system. It's like when some people get a cold and others don't. Please reread the article and you will see how this works.
You don't have your location in your profile, but since I don't recognize the meds you have, I will guess it's not in the US. Since you already have MelaFix in the water and it isn't helping, if your meds are for Bacterial infections, I suggest you use them. If not, wait and get something tomorrow, but don't waste any time because it could get worse quickly.
But, I do recommend a big water change right now.