Ranking sudden Dropped last month on 24th aug to 28th Aug

I have a website related to sweep stakes. I started working on it last 3 months ago and after doing a very little changes in on-page all the keywords (around 50-80) were started ranking in top 10 and improving in a natural way but sudden in between 24th to 28th there is a drop in all ranked keywords are most went down on 3rd – 5th page in Google. Simultaneously there is a drop in impression in webmaster. But i shocked when i checked that there is no difference in Organic traffic. its still…
Ranking sudden Dropped last month on 24th aug to 28th Aug

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