Bluebird Blues

I was a bit excited when I found out that we had bluebirds nesting in the birdhouse.  We hadn't had them in the birdhouse since 2002 because of house wrens.  I had hope this year.  And the hope failed me.  Two babies were born on Friday and Saturday morning came...I check to see if the third egg had hatched and the two babies were m.i.a. while the other unhatched egg was on the ground.  This had happened before and I am just not sure why.  I had such hope.  It looked like the couple were trying to build a new nests on top of the new on during the day on Saturday, but I have not seen them since.  Just not sure if I should let it go and see if they go ahead and build another or get rid of the old one all together.  Anyways, I was able to get a few pics on Friday of the bluebird couple feeding their newly hatched babies...I had such hope.