A judge can do whatever he or she wants, so in theory the answer is yes. However, it would be highly unusual for that to happen. The real danger of this would be in a small town court where the "bring in the next guilty party" mentality rules the court and there is far less scrutiny applied to a judge's actions. Again, having worked in that type of environment (i.e. small town), a reduction in fine is infinitely more likely than an increase in fine.