I have a question, not too much of a concern, but I made a starter for a 10 gallon batch I brewed yesterday. The starter was 1000 ml and was pitched into two separate carboys. Both are in the chamber @67-68*. One is chugging like no tomorrow and one isn't. Both have tilt hydrometers in them and the chugging one is consistently reading lower gravity than the other one. I've noticed this on all 10 gallon batches I've brewed. One chugging and one lagging, but both beers end up tasting the same. What causes this?