17d. Words repeated on top of Petri dish? (7) Not sure if any of the letters I have are right. M-N---B
21d. Run across a pirate (5) R---(O) Again, not sure of that last letter.
23a. Grave robber's concealed state (4)
Once this BLHC is completed, I'm finished, so any help appreciated.
TIA.
Thanks, everyone.
Was looking for the wrong kind of state (condition rather than declare) and had 'double' rather than 'triple' decker. Obviously 'triple' fits the clue rather better.