* A. Phenomenons: The correct plural of "phenomenon" is "phenomena."
* B. Father-in-laws: The correct plural of "father-in-law" is "fathers-in-law."
* C. Pianoes: The correct plural of "piano" is "pianos."
Editors in Chief is already the correct plural form. "Chief" is a singular noun that doesn't change in the plural form, and it's the "Editors" part that takes the plural form.