T.D.
Hello,
My son is 12 months old. He too has become cranky. I agree with the other responses that teething may be the issue. But, I also think it could be a little bit of boredom at times. I think my son has just started to really need a little more stimulation than he had needed a few weeks ago.
I've been trying to switch up our routine a little to keeps things interesting. I feel like at least maybe that helps distract from the irritation of the teething too.