The batch is either infected or not infected. There is no partial infection, unless it;s in the bottles. With that said your bottles are either clean or dirty. If it's the latter then, you could have some infected bottles and some non infected bottles.
I'd agree with Glibbidy...it sounds like more of an issue with bottles over your batch being infected. You can't have a partial infection unless your batch was split between two fermenters. So I'd say its more that you had some infected/dirty bottles over your batch being infected if some are turning out okay.