sleeping more, eating less

K
My baby is 6 weeks today and has been sleeping a lot more and eating a lot less for the past few days.  Is this a growth spurt? A bit worried that she suddenly isn't eating as much. 
Previously she was eating 3 oz pumped breastmilk every 2.5-3hrs and today she's eating about 1 ounce at feeding.  Anytime she wakes up I try again, and she only takes about an ounce each time.