What's infecting my maple pecan cider?

I started this cider on July 14th (OG 1.054) and racked to secondary on August 3rd (SG 1.000). It didn't have any maple or pecan flavors but otherwise tasted like a solid cider. Maybe 10 days after racking to secondary I started noticing some white growths on the top of the cider. They've been slowly growing ever since and I'm not quite sure what it is. I thought I had properly sanitized everything (I've got several 1 gallon batches going and have bottled a few of them already and this is the first infection).

The recipe was 1 gallon of apple juice, 1/2 cup maple syrup, 1/4 lb toasted pecans with Safale S-04 yeast

Anyway, here are some potato quality pics courtesy of my junky Nexus 5 camera:

It looks like the beginnings of a pellicle. I can't see it very well, but it looks like the cider is in a vessel with a ton of headspace. Once fermentation slows, the cider needs to be in a vessel with a very narrow neck, and up to within an inch or two of the bung. It will get worse.