I have found healthy plants are more tolerant than fish are when it comes to meds. They may lose their leaves but bounce back rather quickly. While one bad dosing can kill a fish, I find that plants are a little more resiliant. SHrimp and snails are more sensative to meds especially copper based ones.
I believe the strains of Discus we get now are so far removed from the disease prone wild species that you probably won't have to treat at all. I've been keeping them for 3 years and never treated them for anything. Like any tank don't add new fish too often and make sure you quarantine when you do and all should be well. I only keep my temp around 80 degrees as well. Every plant I've tried seems to do fine also. I change 15 gallons in a 75 gallon tank once a week and use non co2 EI. One pair is on their third spawn in 4 weeks. The other Discus eat them though.