As I understand it, and as what happened with regards to my 1st grains of kefir, it will take a few weeks for it to 'settle in' .
I would try rinsing it in cold water and starting again, I generally use a 1 to 4 proportions of grains to milk.
The type of milk you use also makes an enormous difference. In the winter I use organic milk, which has been heat treated. In the summer I am lucky enough to be able to use organic unpasturised cows milk from a local farmer, and the kefir takes a few weeks to 'adjust' to the change over. But, more than anything else, the resulting kefir drink is vastly different when using the 2 types of milk. The unpasturised definitely has a cheesy taste to it, its quite a fatty milk and it produces alot of whey. (maybe like you, it tastes cheesier because the room temperature is higher in the summer months)
The UHT organic milk I use over winter makes a thicker kefir, and produces only half as much whey, and the taste is lighter, sometimes even a bit fizzy, which I quite like.
Your grains will take a few weeks to adjust themselves to the milk you use, its bound to be different from the milk your supplier used.