Turned a set, is this play weak??

[cl_tc]

Okay, so I was in Laughlin, of all places this past weekend, playing 1/2 NL, 100/300 buy-in, at the River Palms.

I have 500+ in chips.
UTG+1 has about 250 in chips. He's semi-loose and not afraid to bet when he thinks he's got something, otherwise pretty weak/passive. In an earlier hand he PFR w/ AQ and bet strong each round w/ an A on the board.
MP1 has around 300 in chips. He just sat down about 1-2 orbits ago and hasn't played a hand. In the short time I've seen him play I've stereotyped him as an old tight and passive/weak player that I've seen lots of in my play so far in Laughlin.

Preflop:
I get 55 UTG and limp, UTG + 1 raises to 10, MP1 calls, CO or button calls, blinds fold.

Flop (~40): JT7, 2 clubs
Everyone checks.

Turn (~40): 5 (not a club)
I check, with the intention of check raising as I figure the original raiser will try to steal it now, and he obliges. UTG+1 bets 25, MP1 raises to 75 (this freaks me a bit, did he slow play a set or possibly even a straight??), CO/button folds. I calland UTG + 1 folds.

River (~215): blank
I check and MP1 checks.