Super sleepy 6 month old?

My lo just turned 6 months yesterday, and he seems to be sleeping a lot more all of a sudden. Last night he sttn for the first time (YAY!) from 8:30 to 6:15. Then he fell back asleep from 7:30-10:00. He went down again at 12 and he's still asleep... 

He usually takes either two longer naps (1.5-2 hours) or one long and two short half hour naps.  

He doesn't seem sick, he doesn't have a fever, he's happy when he's awake- but then he gets super cranky at the 2 hour mark. He doesnt seem to be eating as often- we just started spreading out his feedings from every 2 hours to every 3 or 4. Is this a growth spurt? I'm getting concerned!