I don't understand people when it comes to FRESH water temperature. In the summer my tank is close to 105F. Fish breed more, eat more, and are more active. All you get is MORE. Ick can't live in high temps. Neither can most other diseases, either because the pathogen can't survive or the fish's natural immune system is MORE effective. You following? Unless someone met me they wouldn't believe the alchemy that is my fish tanks.
Rule #1 there are no rules.
Rule #2 most people repeat what they have heard but with stalwart confidence even if they haven't done it themselves.
Rule #3 like a game of telephone what is repeated is often not what was said. Rule #4 effective hard work produces results. Everything else produces a smell similar to rotten vegetables.
Crank the temp. No temp is too high. These are TROPICAL fish. Their native water temp is damn near 100F at least 10 days of the year ambient in most freshwater bodies. Scared? Do it to one fish in an isolated setting.
Don't simply do this overnight if your tank has been in the 70's since you set it up. You can but you have to shock the water with ice cubes at the same time to get the fish comfortable with fast changing temperature. 5 degrees a day is a decent average.
And it won't have any effect on plants if you crank the temp. You substrate, dosing, or CO2 are the issue if they start melting. The plants will uptake the nutrients faster in certain cases. Be an astute observer and use intelligent judgement.