I'm only guessing at the ph....that's why i like meters. Because your tap water worked for you so far (before you transplanted that is) I wouldn't change it until you know exactly what your ph is......or you'll only make the problem worse and you don't want to screw up your other ones do you?

You can even get cheap ph test strips or drops from your local pet store to test the ph....very cheap.....which will work fine. BUT you need to ADJUST ph with something MADE FOR PLANTS....not for fish.

Ph TESTERS for fish are ok. PH ADJUSTERS for fish are NOT ok for plants. Hope I made that clear.