This is just a thought. I used to see this years ago in my tank. It had to do with ferts bottoming out after a water change. You remove a large amount of water you remove a large amount of nutrients. Some species don't like the dip.
IME Macranda has more nutrient needs than Ammania, so no surprise Ammania shows no effect. If you notice the plants rebound as the days go on it's likely because nutrient levels are coming back.
To combat this many people dose the tank back up after a water change to keep levels stable. Personally I front end load all macros.
Again, just a thought. Could also be something completely different.