Multi Condition M using AND Operator

I'm creating a custom column.  I have 3 fields [FieldA, [FieldB], [FieldC],  I'm trying to write a conditional clause that produces a value if they are all e fields null else another if any of them aren't Null

each if ([FieldA] = "" and [FieldB] = "" and [FieldC] = "") then "All are null" else "Not null"

This isn't producing any syntax errors.  When it runs it assigns every value in the new column to "Not null".  I know there are hundreds of rows where all 3 fields are null so this is incorrect.  I'm so close..  I've tried ISBLANK, it doesn't like it.  How can I do this ?