Its very possible that you made a mistake back then. It happens. you think you set it to sth like 2, but infact it might have really been 16, you trained it with 16 and then sometime later, changed it back to 2 (or maybe changed sth else, used a higher dropout ratio, weight decay, increased or decreased a featuremap, etc) and forgot about it. in order to be sure you indeed ran on batch of 2, look at your logs if you have one.
Another scenario is, the random nature of the seed you use. try using the same seed for your operations and see how that goes.