Typically unbalanced flow between skimmers means 1 of 3 things:
(a) with separate valves, one line may have a closed or partially closed line, OR
(b) the piping to the 'slow' skimmer was laid out improperly, OR
(c) something is in the piping on the slow side, like a rubber two or a walnut.

Finding and fixing problems like these is not, unfortunately, something we can help much with over the Internet. You pretty much ave to work from the pool deck.