[cfjr2]

grunch
PF 5sb|flop 15sb|turn 11.5BB|river 13.5BB to you

I think you should have bet the turn since you raised the flop - if your hand was good then it is likely still good now (except against a T9 - or a donk played Jx). Since you didn't and you called you have to call down unless you know you're not good 1 in 13 times (~7%).

you checked turn so UTG made a play for the pot - no one believes a PP here and they all have overs

UTG+1 figures his 7's are shakey - you raised so he thinks you may have something on the flop but he will call down,

then you check turn so he figures you're on a bluff but UTG bets so he thinks UTG hit 8's

then river goes check check and he figures he may be good, bets the "I have a 6 for the donk str8" and gets better hand(s) to fold.