kefir newbie

I started with kefir grains last week. All i can produce is milk that tastes off!!!! i've followed instructions found on the net and still think there is something wrong.

i use 250-350 mls of uht or fulfat cows brewing for 8/12 hrs decant this into the fridge for 24 hrs. its not as bad as off putrid milk and only has a very mild smell to it.

it this what is supposed to happen???