@Natalya oh wow I didn't know this!
It definitely could be because of breastfeeding but I feel like at this stage it wouldn't be causing the light then heavy period but take what I say with a grain of salt because at the end of the day I'm not a medical provider. I found some books by Alyssa Vitti- she is an obgyn and founder of cycle synching " women code"and "cycle synching" are her books. And essentially she speaks to how our hormones impact each phase of our cycle and why. She also goes into detail about irregular or missed periods. Ever since following her protocol my periods have been regular and "normal".
Remember when you have a period you’re switching I think it’s your ovaries? So one may just have a heavier period than the other it’s normal. Before I had kids my period would be like that too