Zed Secret nerf??

I had 60 armor Pen from runes/Masteries/Items 400 ad, was attacking a 65 armor mid squishy, was only doing 120 basic attack dmg, and 300 ability dmg, and ult dmg, plus hit, but my execute was only 690 instead of 1189 or 1500 like i usually get,

Time:Today NA Zed Shockblade Skin 60mins Normal Game Ping 65-700 ms fps 80