Custom CSS overridden by ???

I am using a custom template designed off of twentytwelve. The blog is here – https://ritualconditioning.ca/rcblog/ – and *used* to look like the rest of the site – https://www.ritualconditioning.ca. Blue header area, yellow menu bar (which used to line up with the background), white main content area with a 63% left column, 31% right column and a dark blue footer area. Everything was great for a while.

Then we were trying to resolve an issue with posting links to FB, and (best guess) one of the plugins we installed must have overridden my css with theirs. Hence the out of alignment background, the lovely grey background in the main content area, and the very narrow left/right divs. (Note: it hasn’t seem to have impacted the mobile phone version of the page, just the tablet and desktop ones.)

I have turned off all the plugins to see if that would resolve the issue, and thus narrow down the cause of the issue, but that made no difference. I have checked my css and it appears to be the same as it always was. I have gone over the ‘view source’ on the page and see that the plugins have added a bunch of crap, but for the life of me can’t figure out which one is causing my issue.

If anyone smarter than me out there can help me figure out what is going on, I would greatly appreciate it.

Thanks, and happy new year.
Alison