The rules would be up to Dexenthes but my recommendations are no more than 3 guesses at a time per person until Dexenthes says yay or nay. Then a person can try more guesses.
Example:
Not ok:
MemberA - 3 guesses
MemberB - 3 guesses
MemberA - 3 guesses
Dexenthes - Nobody yet
Ok:
MemberA - 3 guesses
MemberB - 3 guesses
Dexenthes - Nope
MemberA - 3 guesses