The property is in the Central Valley of California, so not a humid area.  

If you're painting in your shop, and it's not climate controlled, the primer needs to have some extra time to dry out during especially humid times.

Now in Tennessee I would still keep the vapor retarder to the interior side due being north of the "Warm-Humid" zone defined by IECC Climate zone map.  

Florida has humid climate & hurricanes.

The humidity is crippling. 

Instead all we got was a humid heat wave? 

Exterior finishes are one of those things that vary by region, depending on the humidity, etc.

There is a persistent problem with rising humidity in the walls, causing peeling paint and ease for mold to hold on to anything you hang on the walls.

Check to see if there's ducts upstairs. couple of things a good HVAC guy should've tested:  i would use a psychrometer to test the humidity in the air.

The caulking will expand/contract with changes in temp and humidity, and as building materials shift over time.(4) If you don't know the grout color, and it isn't a straightforward bright white, etc, tear-out and re-tile will give you the best overall finished product (and will likely allow you to determine the issues causing the cracking).As a general rule of thumb, it's best to purchase grout and tile caulking for all tile jobs (when starting from scratch).