@AastroGuru I appreciate your concernā¦ 
And yes I want to know how to calculate Optionā¦
I have edited my post above and included the calculation part.
Good Luck!
thank youā¦
In this case both theta and Implied volatility might have worked againist you, when vega decreases premium also decreasesā¦ But what was your theta on the long put position then? if you know that then you subtract it with the move and calculate how much of the downmove was caused due to vega? If anyone has any other opinion on it then kindly give your thoughts upon itā¦