Let it go or balk?

[tornado]

I was doing a 14 year-old tournament this last weekend.

1st game, early in the day, R2 leads off. F1 tries a pick-off, and the ball sails into center. R2 heads for 3rd where he's gunned down by F8.

Late in the day (my 3rd game), I have this team again. R2 leads off. F1 tries a pick-off, and the ball sails into center. R2 heads for 3rd where he's gunned down by F8.

Deja vu?

After the 2nd time, it was looking like this was a planned play.

I called nothing but the out at 3rd both times.

If you saw this multiple times in a game would you let it go? Would you call a balk?