Unfortunately I don't have much to add to this, but I do think it is an interesting discussion. I too have noticed that plants seem to have their leaves out a bit more later in the day after water changes. When I switched to mainly RO water (~15% tap, sitting out for several days) I expected it to go away, but it didn't. There isn't much in my water, but the plants are exposed to air for a while and there is a ton of splashing when I put the new water in. Perhaps several of these conclusions are valid which is why removing just one doesn't stop the phenomenon?