First time making cider. I pressed about thirty gallons of cider with the help of friends and froze it before I decided to try to make hard cider. I thawed 4 gallons , and placed the cider into 4, 1 gallon sanitized jugs. I added 1/2 cup brown sugar to 2 of the jugs and a campden tablet to each of the jugs. After 24 hours I added approx. 1/4 of a packet of D47 yeast. The primary fermentation took off well with OG of 1.055 to 1.065. I racked to other gallon jugs after 7-10 days with a gravity of 1.002-1.004. I attempted to make up the volume lost with marbles, boiled, cooled and sanitized. There still was some space on the top of the jugs but it was better than nothing. After about two weeks in secondary I'm noticing what looks like dust on the surface of the cider in a couple of the jugs. The air locks were filled with vodka and though there is no bubbles coming from them there is pressure there shown by a difference in liquid levels in the air locks. Is the " dust" I'm seeing a problem? I used starsan for sanitizing everything touched by the cider