not getting the right amount of crystals for temple runs t15

ive been farming t15 6 mods for the past week now and everytime i complete a vaal ruins encounter ive been getting 1 crystal for a majority of the time, 2 every once in a while, it took me about 45 maps last night to get 60 crystals, 45 maps is ridiculous. i thought i was supposed to get at least two per 6 mod t15 map.