tired? bored? teething? why the crankies???

My 4-month old darling baby girl who has up to now been pretty laid-back and happy, especially in the mornings, has now had 2 fussy-cranky mornings in a row following 2 nights of waking 3-4 times for food. Previously she was sleeping for 6-8 hour stretches and has always been a really good sleeper - even as a newborn she was not up more than twice per night. I'm exhausted and at a loss to explain this sudden change. She's suddenly started using her hands a lot more and being way more interested in her playmat, and she is distractable - I can stop her crying by picking her up and walking her around, but she's crying at EVERYTHING now. Like being fed when she doesn't want to be, or being on the playmat when she doesn't want to be, or just sitting on my lap, or whatever. What's the deal? Is it just tiredness from waking up too much at night? Is her mental development outstripping her physical and she's getting bored because she can't play with enough stuff? Anyone else have this happen? Is this typical teething behaviour? And most importantly, any ideas on how to get my happy, sleeping-through-the-night baby back?

(The upside of this is that she's eating less during the day. She seems WAY less hungry in the morning... maybe I should not feed her during the night when she wakes up, just try to get her back to sleep with rocking or something? She is actually hungry though, she has a good 20-minute to half hour feed when she wakes.)