Why does white bread have mold faster than wheat bread?!
Answers: White bread has refined sugars in it while wheat bread has more complex sugars. Mold grows faster on white bread because it doesn't have to work as hard to get at the sugar.
It is difficult to give you a precise answer to your question without some
more information about the breads you used. If you still have the original
packaging, you may want to check to see if they have the same experiation
dates. It is interesting that the wheat bread has no mold after 30 days -
that is a very long shelf life for bread. You will also want to compare
the ingredients used. I suspect the wheat bread has additives such as
propionates which are used to prevent mold growth and increase shelf life.
It may also be that your wheat bread has dried out, leaving moisture
levels too low for obvious signs of mold growth.