Deck is sagging
DH is installing deck boards and has found that 6 of the 7 the deck beams sag 3/4" at the center. The beams are 2x10 that span approximately 12'. The intermediate supports weren't installed well - they are nailed in, but there are lots of gaps.
The easiest fix would be to jack up the beams and fix the intermediate supports so that they tie in better, but we're not sure that would solve the problem. Other options are to leave the beams alone and shim the deck boards, take the beams down and flip them over, or replace the beams with 2x12's.
Any advice would be greatly appreciated. Here are some pictures of the beams: