Why does iTunes prompt me for family organizer's apple ID and password when updating apps?

Before iOS 8, I used my wife's Apple ID to purchase iOS apps and install them on my iPhone.

When iOS 8 came out, she set up her ID as the family organizer, and I started downloading apps using my Apple ID. I went through all the apps in my iTunes library and re-downloaded them under my ID.

However, I still occasionally get prompted for her apple ID and password when I update apps in iTunes (using "Update All Apps" button). I type in my apple ID and password, and the update downloads normally for that app. However, this is annoying because it stops updating other apps that appear in the list of apps with updates until I click on them and update them individually.

(a) Why, when I have already redownloaded all apps under my ID, does iTunes occasionally prompt me with the organizer's (original purchaser's) apple ID?

(b) Is there something I can do to keep my current iTunes library and get all the apps marked so it prompts me for my password?

(c) This is only slightly annoying for me, but for my children's accounts/libraries (similarly converted from sharing apple ID for purchases to using their own with family sharing to get all the same apps) it means we have to type their password twice for each app that hits this update glitch because it won't save the password for under-13 accounts.