ammo missing from boss fights

this week I've noticed when i do boss fights when i go back to do another that the bosses have lost some of the ammo that i put into them. IE I do 104000 damage I go back into bosses later and there is only 88000 damage so I have to use more ammo. Today it did it a lot which is why I bring it up. Usually its only 1 or 2 bosses today it was way more.

Tommy, If this happens again, please give us an exact instance of this occurrence, with as many details as possible: who initiated the Boss fight, times, damage done and anything else you think might be important. Thanks.