Why does entering 1099-Q info for 529 plan distribution increase taxes when I used $ to pay education expenses? And entering one kid's 1099-Q does this, but not another's

I have two kids in college, each with a 529 plan. I made qualified withdrawals for each and used the money to pay tuition. The entire withdrawals, much less the earnings, were less than the total education expenses paid. When I enter the 1099-Q for one kid, my taxes do not change. When I enter the 1099-Q for the other, my taxes increase. Both kids have 1099-T info entered. 

The earnings withdrawn from the 529 should not be taxable, but TurboTax increases my taxes as if the withdrawals from one of the kids (but not both). 

Help!