Decreased indexed pages and drop traffic in last week

[digiboy]

<My website> is based on Wordpress and has 250000+ content pages .daily indexes is over 300 when i search site:mydomain.com for last 24 hours .
the traffic droped on main keyword terms after penguin updates and first or second search positions droped to 10 and lower !
from last week the indexed pages on site:mydomain.com decreased from 100,000+ to 61000 also decreasing daily !
website have no problem on structure and we don't made any changes on it .google webmasters and other SEO checker tools didn't reports any problem too .
please help me .
thanks a lot .

[edited by: aakk9999 at 3:57 pm (utc) on Sep 19, 2013]
[edit reason] Removed specifics [/edit]

[goodroi]

What is the average word count on these 250,000 content pages?
What systems are in place to handle duplicate content issues?

[digiboy]

contents are advertisements sending by users and may contains between 10 and 500+ words in each post . so we could not handle duplicated contents because of large amount of users and post .