Mistakes with your pH, EC and temperature can cause real dramas with your poor plants. Their roots become accustomed to certain conditions and don’t always adapt readily to change. Always use the same water source when mixing your solution to maintain consistency. Temperature shock is also an issue - don’t pull plants from warm solution then flush them with icy water once the change is made. Imagine a cozy bath that suddenly turns chilly just as you start to relax and you’ll get the picture. This is beyond the more obvious problems with spills, leaks and the hard work itself that comes in a water change. I’d be lying if I said I’d never damaged a plant during a hasty top-up or water change. It pays to take your time and treat your rig carefully.