Syrupy Water Kefir

Hi all!
I've recieved some water kefir from someone I found on the web and have been trying to brew some for myself. At first things seemed to be fine. I was using Muscavado Sugar and the results seemed pretty good. However it wasn't bubbleing. The first batch or two got some fizz after being stored but that soon stopped.
The kefir became thick and syrupy, which gave me digestive problems when I drank it. I also ran out of muscavdo so started using brown Sugar and molasses. Still syrupy. I cut back the amount of sugar, and soon the kefir was bubbleing away, but the water still turned syrupy.
I've now washed my grains, stored them in Sugar water for a week to rest them, and am now trying again. This time I'm only using White Sugar and unsulfered sultanas.
Here's my theory. I've read that syrupy kefir comes from the grains having too many minerals. The guy I got the grains off said he was using filtered water, which I know removes most if not all of the minerals. I'm just using tap water. The tap water here in Berlin, DE, is very hard (>14) and has no added flouride. The chlorine level is laughably low, but I leave the water standing overnight just to make sure.
So, is it possible that the combination of both very hard water and the molasses has given the kefir more minerals than its used to? Does it maybe just need time to adapt? Am I doing the right thing by just giving it White Sugar for a while? How do I know if the grains are simply no longer viable?
At no point have I witnessed any growth, and i'm not expecting to see any bubbles for a while as they have just come out of the fridge.
Thanks for any help you guys can give me. I'm a total beginner to water kefir. I've never drunk it before, so i also have no idea of what it's supposed to taste like.
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