Castrum Meridianum : No extra Tombstone after finishing

So i reached level 50 and am working on my dark light equitment by farming tomstones of mythology.the thing is i got weird since yesterday.before i got 120 tomestones for finishing every time ,but now it is random .sometimes i get the 100 tomestones from the boss and sometimes not.am i doing something wrong?:confused:

You only get extra if, it is the first time someone in the group is clearing, or if you are doing the duty roulette for the first time that day.