Newbee question, I brewed an SNPA clone last night and pitched 1 packet of Safale US-05 directly on top of my wort as the directions stated on the packet. My pitch temp was 70*, my ferment temp cooled to and is holding steady at 68*. (primary temp not ambient) This is an extract brew using 7lbs of DME and 1 lbs of Crystal 60L. I am 24 hours in and see no signs of fermentation, no bubbling and peeking through the airlock grommet I can only see some foam on top, no change from when I pitched seemingly. I aerated prior to pitching, did not rehydrate or stir. Do I need to be concerned at this point or just wait it out another day or so? Expiration date on packet is 2015.