If the eggs are not losing the proper amount of moisture, you may need to change the relative humidity. Many producers maintain several incubators at different humidity levels and move eggs as needed. Others cover parts of the shell with tape or fingernail polish to reduce water loss, or sand away part of the shell to increase water loss. These practices are easy with a few eggs, but become impractical when more eggs are produced. Their effectiveness is unproven.
Many growers routinely wash eggs with water and sanitizers.
However, it is best not to wash eggs. Instead, set only nest clean eggs. Fumigation of eggs with formaldehyde gas is becoming rare due to health risks and government requirements, and, therefore, probably should not be used. Many growers use disinfectants prior to incubating. It is important to follow instructions that come with these products to avoid potential disaster.