Why? Back to short naps

My son has always struggled with short naps up until a couple weeks ago when he started taking longer naps (1.5 hours or so). Well we traveled last week for thanksgiving and he took great naps on our travels, but now that we are home it’s back to 30 min naps. Can anyone tell me why? He’s not teething that I can tell, but he may have some gas. I was not eating a lot of dairy before, but I didn’t watch myself over thanksgiving. Could it be his stomach?