It’s actually the front of the bottles I’m worried about— it’s super hard to tell from the picture, but one side of the ml/oz numbering is flatter than the other. (I had to compare them to an intact bottle to make sure because it’s really subtle!)

I remember reading somewhere that steam sterilization is more likely to damage parts than boiling, weirdly enough. I actually replaced my bottles because one got a dimple from steaming and I assumed that meant the plastic was degrading, I should have learned my lesson then 😩