over the long run it shouldnt be question of luck. but the ideal count give me 2x more, that makes me suspecting. didnt say its pool. can it internet connection or something else
Sounds like you had some downtime on your miners. Maybe internet connection down, or power outage, or something else. Have a look at organofcorti's profitability charts. If the pool was paying out just 50% of the expected average then the charts would look much worse.