Automatic Variable Change?

no, they will despawn because of:

if (bulletYs[i] == 0 && bulletXs[i] != 0) {
        Serial.println("BAD BULLET BOY!");
        bulletYs[i] = 0;
        bulletXs[i] = 0;

      }

Which basically removes them from the list and all their data, so despawn(well, at least, that is what is expected to happen)