I'm about 5 days into fermentation on my cider and I noticed the water in my 3 piece airlock starting to get close to flowing backwards. 1 gal carboy, 3 cups sugar, 1/5 vial english labs cider yeast, 1 teaspoon yeast nutrient. It gets a little cold at night, maybe 62-64. When I noticed this it was about 68 in my house. Any ideas what could be causing this?