I believe you have laced the wheel incorrectly. Follow any two almost parallel spokes that are going in the same direction from the hub to the rim. One spoke is coming from the right flange and the other spoke is coming from the left side. You will notice that the holes in the hub are not lined up across from each other but rather they are offset. That means that the head of one spoke is behind the other spoke as you are looking straight down as they come out of the hub. As you follow these 2 spokes going in the same direction out to the rim, the spoke that started behind the other one at the hub should also be behind it at the rim. It looks to me this pattern got switched and the spoke that is ahead of the other one at the hub got behind it at the rim. This is why one is tight and the other one loose.