Did John Marshall actually served as Secretary of State under TWO presidents?

No, although some sources curiously show John Marshall remaining in office until a date in mid-March, 1801, which would have meant he also served under his political enemy, Thomas Jefferson. In fact, Acting Secretary of State (Madison was delayed in taking office) and US Attorney General, Levi Lincoln, threw Marshall out of office just before midnight on March 3. Marshall had already been sworn in as Chief Justice of the Supreme Court, and continued in that role upon leaving the Executive branch.