Pls help - What are these dark spots?

I made my baby some purée with canned salmon, frozen strawberries, sage and some oat cereal to thicken it up. Things got hectic and I wasn’t able to wash her stuff right away so it sat for a few hours and when I went to wash it there were all these dark spots?? I googled if it could be mold but what I saw said a few hours isn’t long enough for visible mold to grow. Anyone know if one of the ingredients oxidized or something? I froze the leftovers when I made it and now I’m worried I shouldn’t use them or that I need to sanitize her bowl & spoons.