I would jam i think you are getting called by a lot of 4's and pairs with a big diamond. The utg limper i think will limp pre with J4 Q4 K4 A4 and will raise these on the turn J4 being the only boated hand, 6 combos of boats for utg and 24 combos or trips and possibly more if he called with 46 45 etc. also i don't think the BB will check 99 on the turn when the board pairs and the obvious draw came in, he more likely to do this with Jx hands check calling top pair with a KQA of diamonds kicker in his hand, without a specific read that tells me i'm beat here i'm jamming, you could even get called by 2 worse hands.