Just coincidentally, we have 2 or 3 pairs of Black Chins hanging around this year (usually they are gone by early spring). The birds in general seem to be much more aggresive toward one another too. Usually we have just the Rufous by this time of year so I'm wondering if it is the 2 different species going after eachother.
if you're getting more birds staying longer, perhaps you should consider getting a couple more feeders. I know some folks that let me photograph the hummers at their place, and they have all 3 species common to eastern WA (Black chinned, Calliope, & Rufous). There are about 25 to 30 hummers in all at their place, and I've never noticed any fighting or dead birds. They have about 10 feeders that they keep fresh sugar water in at all times, so the birds aren't competing for the same areas.