Gravity Increase after Cold Crash/Purple Yeast?

Hey,
So I went to keg 3 batches of cider today and right before pumping into the kegs I decided to take another gravity reading, thinking it wouldn't change and if it did that it would go down slightly. To my surprise, one of them went up 4 points and the other two went up 3 points.

What would explain a gravity increase after crashing?

Also, there was a mistake made when I put a pear cider into 1st, and that was that the blowoff tube came out of the bucket of water, leaving it open to potential for bacterial growth. I noticed in the yeast ring around the top of the carboy that some of the wet yeast looked very slightly purple, while the dry yeast right next to the wet was tan/brown as normal. It just makes me wonder if something has gotten in there and made it potentially unsafe to drink. Thoughts?

Thanks!

What would explain a gravity increase after crashing?

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the temp of the juice is colder

CvilleKevin said:

the temp of the juice is colder

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That was what I was thinking. Did you temp correct both readings?

As for your purplish yeast, I doubt it's a problem. There isn't much that can survive fermentation that will hurt a person.

EDIT: On second thought, save some of that purple stuff and run it by it's self. It would be extremely interesting to know if that was something that was living, or just a color compound that concentrated from your cider.