Air in Lines

Hi, when I woke up this morning our pool system was sucking air and had bubbles in the pump and the skimmers were not full of water as they should be.  Basically, I have air in the system.  The water level is fine in the pool, the o-ring on the strainer basket by the pump seems to be fine.  I didn’t check the o-ring on the valve going to the pump but it just happened over night so it doesn’t seem that would be the issue.

We did just get a variable speed pool pump last year.  Up until this week I had basically run it close to the high speed but have been playing with it a little bit.  Can a variable speed pump cause air in the line?  We have a 30,000 gallong pool, Beginning at 8:00 a.m. I run it 2600 rpm for 12 hours, then from 8:00 p.m.-7:00 a.m at 2000 rpm (this is the lowest I can go w/ the chorlinator still working) and then I do a quick clean at 3450 rmp for an hour before getting back into the 2600 rpm.  Any ideas if this is contributing to my issue?  Any input would be great.  thanks!