Our pool pump lost prime. We have a newly plumbed, in-ground pool for 1.5 years; it is 20k gallons with 2 skimmers and no main drain. Pool has been working all summer, then suddenly, only the right skimmer is able to hold prime. When I open up the valve to use both skimmers, the pump will no longer hold prime. What I’ve done so far was 1) added water to bring mid-level of skimmer; 2) checked plugs and lubed o-rings; and 3) cleaned DE filter. Several times, I’ve tried to reintroduce left skimmer once right skimmer has been fully primed with no success. What am I missing? Appreciate your help.