Hi Jaime,
My LO has just turned one and we are also on one nap a day, and I've been going through something similar with her. She started waking at the 30min mark in her naps and at night (as well as NWs, EWs, short naps, hysterical crying...you name it, we've had it!). I believe it happens from OT, and especially now because the 2-1 switch can be a pretty tough transition. She did really well for the first couple of weeks but then everything went bottom up. It looks like things have started settling down again, but now I'm prepared and almost ready for them to mess up again and for this to keep happening at least for the next few months.
Also Ella just had 2 teeth come through in 2 weeks, so I think that may have played a part in messing up her sleep.
Hope that helps!
Michelle.