If you remove the bearing and wash them you will see if there is any problem with the cup or bearing.. The bearing has a O on the large end.. it is the wear bar.. if its worn flat then the bearing was over tightened or just worn out.. The most common thing on the rear bearings is to over tighten them and burn them up.. However when you remove the rear bearings in most cases you damage them so they will need replaced ... You can check them by checking the end play.. They should have about 2 thousands end play.. perhaps up to 4 but not much more.. however you should have checked for that when you put them in.. There are also a number of other things that will cause noises on corners.. so if the end play is right I would just leave them and check them from time to time.. If it does grow a lot it will mean it has a bad bearing..

Ken