Need more information to really help..how many fixtures were on each circuit, is the panel serving them 3 phase, were the circuits sharing a neutral?
Shared neutrals are a big no-no with ballasts, especially electronic ones. Harmonic currents add up rapidly and cause no end of problems and repeated ballast failures.
And any loose connections can kill e-ballasts rapidly. Had one case personally where we went through 3 ballasts on the same fixture until I pulled on the whip and the loose wirenut fell off in ther j-box. Fixed that and no more failures since (about 6 years now.)
