Perfect Storm?

I changed my withholding last year to Single 0, My wife changed her's to Married 0 -- Because we got hit with a 1,600.00 owe for both Federal and State.  In the past, we usually got a refund.  This year it jumped to 4,674? -- we just don't have that kind of cash available to meet this obligation.  Did I do something wrong, seems like a big hit.  The only thing I can think of it my soon to be 21 year old son, we no longer can claim as a dependant.  My 23 year old daughter recently graduated from college in June and got married in August, we no longer can claim her or get the tuition credit.  In addition, I received just over 4,000 from a retirement plan.  Our income and adjustments were 153,759 taxable 129,359.  Hard to believe we still owe so much.  Any ideas or suggestions?