I would think if all 3 goats have the abcess then the breeder's method of vaccinating is causing the problem. It is most common when the vaccine has been allowed to expire and if a separate sterile needle for each goat is not used. If it were me though I'd still be getting it tested, it just isn't a normal injection site, and a softball sized abcess I've never seen in 10 years of vaccinating alot of goats. And I'd also make sure they get fresh CD&T's since their last one might not have been effective if it was an expired batch.