Just post a picture of the rocks on here and we'll be able to tell you whether it's safe. Practically all rocks are fine. Even limestone would be ok if you had african cishlids.
The Vinegar test is pretty bogus, because vinegar is a really weak acid and it's hard to tell the occasional bubble formed by a reaction from one escaping from the rock. Testing for the presence of calcium this way is mostly an old wives tale perpetuated by people who've never actually tried it. Yes, if you stick a sea shell, which is pure calcium in vinegar you will notice a few bubbles, but with rocks it's not the way to go.
Just stick with basalts, granites, and slates and you are guaranteed safe.