Weird C-String

Hi Guys!

So I decided to learn the ukulele and the next thing you know I bought a relatively cheap Lanikai pineapple soprano. It's been tons of fun over the past two weeks. The intonation isn't perfect but it is nothing noticeable. So all has been well until I switched the stock GHS strings to Aquila's. The strangest thing has been happening, ever since I've restrung it the C string gets sharper. Not sharper as in as I go down the frets, but when I let the uke sit all the other strings go flat and the C string goes sharp. It goes sharp relatively quickly. I'm new to all this but don't strings usually lose tension when they're settling?

I had the same thing happen to me. im not sure why. my only guess is that the drive home they were sitting in the sun and got real soft. I ended up having to get a new string because i cut the extra off. (yet another reason to wait to cut your loose ends =P )