Day 5 and day 6 embryo transfer

I have two day 5 embryos and 2 day 6 on ice. My dr wants to put back both day 5 in my fet scheduled for Jan. I have had 5 failed transfers and no ERA. I also have weird side effects to meds that can’t seem to be explained. For these reasons I would prefer putting back one 5 and one day 6.

My husband thinks this isn’t possible since they were frozen on different days. I can’t see why not since both are blasts and at the same point now. We can’t remember if the dr said anything at our consult about this.

Does anyone know if I could transfer a day 5 and a day 6 at the same fet??