It looks like Sunny is way past birdie puberty. How long have you had him? By the cere coloration, it looks like he's a good few years old. As well, it looks like Cloudy is a moderately aged female. A few things come to mind:

1) Are Cloudy and Sunny living in the same cage? If so, bird friends are much more pleasing than human friends. Naturally, Sunny would choose Cloudy over you (mine do as well, but I don't mind). This wouldn't explain his abrupt change in behavior, however. Has this inclusiveness been going on for an extended period of time or was it just a sudden onset?

2) Though it's not very likely, Sunny may be going through birdie puberty. It all depends on what his age is. However, it could be an influx of hormones now that it's Springtime.

3) Have you been interacting with him everyday for the past months and years? If you've been leaving him alone just for a few weeks, he can still reverberate back to not liking humans.

4) Health problems are always in the question, but this probably isn't very likely.

My suggestion is to separate Cloudy and Sunny and interact with him individually. Keep feeding Sunny seeds from your palm and entice him to leave the cage. If you're up to it, I would highly recommend clipping his wings. Have you read Guide to a Well-Behaved Parrot by Mattie Sue Athan? It's chock-full of simple games to play with your apprehensive parrot.