Looks like you're using the same builder I am ... The drop in water pressure was most likely due to the plug inside the skimmer popping due to heat. If so, it's nothing to worry about.
It happened to me the evening they did the gunite, while I was standing outside. It was quite the loud "pop", and the lid of the skimmer (which was tapped down) flew off and a column of water shot up. I contacted the construction manager and he said it was just the plug which popped, and happens quite a lot when building pools in the summer around here.
When they get ready to pressurize the system, they insert a plug into the hole on the bottom of the skimmer, to seal off the inlet. This isn't there when it goes into operation, but is needed to hold pressure during the plumbing check.
Take a look inside the skimmer, and I bet you see the plug dislodged, and probably a large O-ring laying in there too ... or, if it was like mine, the O-ring flew out of the skimmer and landed in the pool shell.