Where are the hummers? and other birds?

Something very strange is happening, something that doesn't make us happy.

Our hummingbirds have, so to speak, flown the coup. 

They are gone, all of them. 

It happened while we were gone for a week.  We left plenty of food, as we always do, but came home to find the food hardly eaten.  Usually they stay until the first of July.

When we left the hummers were flitting around our feeders like they usually do--several of them bopping on and off of them, fighting for space, etc.

And now?  Nothing.  We've seen one in the past 10 days or so, probably an Annas, not one of the Rufous that had been here.

Where are they?  Has the weather been too cold and wet?  Is it something else?  Is it something we said? 

We also used to see our tropical birds by this time. We saw one (ONE) goldfinch 8 days ago.  And none since then.  All we see are the birds that stay here year round.

Does anyone know what is happening?  Is this something to be worried about?