Determining if I have an infection problem

Okay I think I've picked up an infection from doing a fruit beer.

Did a Blueberry Wheat, secondary w/ 3 lbs blueberries. I dunked them in boiling water for about 15 seconds to kill off anything then I mushed them and racked beer on top. This beer came out tart/sour tasting.

I think i fermented a belgian blonde ale in the same bucket. It didnt finish dry enough (1.016FG). Now it tastes sour and cloying after being in bottle for a week. Used White labs trappist ale yeast.

I brewed a belgian dark strong ale and pitched it on yeast cake from above and it seems to of over attenuated (1.017 and still fermenting)

Do any of you think its possible I picked up an infection from that fruit? Or is it just the flavor of the beer and the belgian blonde just didnt dry out enough as a result of underpitching?

Edit: None of the bottles have been gushers. In fact the blueberry wheat has had a problem carbonating.

is it a fruity sour taste? if so its probably the berries. if it taste like sour dough then its probably an infection. i wouldn't be that concerned about the over attenuation. its just over fermented giving you more alcohol. it might be fermenting the sugar from the fruit. hope you added Pectin enzyme otherwise the beer wont clear.

personally to pasteurize fruit i boil about a gallon of water for 10-15 min. then let it cool to about 170. then add the fruit and let it sit for another 15 - 20 min.