It might just be the curds and whey separating ... sometimes mine will do that and I just give the jar a good shake (but be careful opening it afterwards ... it might "spit" some out as the cap comes off). If this is the first batch with some new grains, you may want to dump it if you aren't sure, and then the 2nd batch should be good to go. But, separation isn't a big deal, and might actually indicate as well that you kefir'd the milk too long (or long enough depending on how strong you want it). At least that's been my experience - I can tell that my batch went a bit too long with the grains if it separates easily (though I don't like mine too strong). HTH somewhat.