Witching hour = low milk supply?

My daughter is 3 weeks old and has this “witching hour” from 5pm-9pm where she is inconsolable. The only thing that calms her is cluster feeding the entire time.

My pediatrician told me it was due to my low milk supply (she is also not gaining weight as fast as she should).

For those of you who have successfully EBF did you have moments like this? Witch hours? Or purple face crying? Or is it really just those of us who aren’t producing enough milk?