Why does my iPhone 6 alarm clocks not go off?

I have 6 alarms set; 5:00 am, 5:20 am, 6:45 am, 7:00 am, 7:15 am, 7:35 am. All of them are set to go off every weekday. I depend on them to get up super early for showers and whatever. Well sometime they don't go off, and I thought maybe they were going off but I was turning them off in my sleep but today I was laying in bed, not asleep but with my eyes closed and waiting for my 6:45 and it just never went off! I checked and it is set for every weekday. And it's not the volume because the 5:00 am one I heard and my 7:00 am one I heard

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