With a few of ours that did that we dripped water onto the shell and put like a drop or two on the pip area that seemed to work for us.How did you set the fan? DOes it blow toward the ceiling/ wall OR onto the eggs? It should not blow on the eggs, just rearrange it later. For now shut off the fan if it blows on the eggs.
I find if an egg takes a long time from pip to hatch, it is more likely to have drying out problems.