It's best to use the grains in whatever they were used in to begin with...
Never wash the kefir grains, you can rinse them in stuff, but not in tap water-chlorine, and other chemicals will affect them.
I use one batch of grains only to ferment grape juice, and another only for milk.
Even if they get all clumpy with milk solids, I only gently rise them in milk.
The fruit juice grains I "rest" in between batches in 10%sugar solution.
Watch your grains for a few days, maybe they'll recover, but I think you may have to get some new grains.
Most of us have killed grains oe time or aother...:)