Transportory Stone gone

I have had about 6-8 transporting stones built around the isle of siptah on a pve server for about a week now. Today I log in an only have 3 portals. My purge meter is still in the same spot and hasn’t budged so why have my hard earned portals been deleted?

Have u checked ure log? They couldve enterd decay state and decayed if not on proper foundations (remeber things decay faster on ground than on a goundation)