<<<In effect the announcement brought it down, but why didi it drop below the offering price? >>>
Market conditions. They picked the absolute worst day to announce and commence a secondary, IMO.
We know that MLP's do secondary's periodically...that is life. But, geebus, FGP's luck with this one was pretty bad. Nice price action on Monday, announce secondary, and Tuesday the world markets all tank...so it was a double whammy downdraft for FGP. It'll recover though. The nice distribution will lure buyers.