graphic

last month i bought 4 ngk copper spark plugs heat range 7 and i had them gapped at .030
they have about 200 miles on them and yesterday i wanted to check up on them
and i noticed that they (all 4) have a a split in the middle of the electrode...
it starts at the top and continues about a 1/4 of the way down...
they still work but i was wondeing if they came like this or if they are supposed to be like this or if they are now messed up...
i am running a stock ignition by the way other than a msd btm at .5 retard and
5 pounds of boost on a 98 lude

do you think my gap is to tight...what on earth could have caused them to split