If \( \alpha, \beta \), where \( \alpha < \beta \), are the roots of the equation \( \lambda x^2 - (\lambda + 3)x + 3 = 0 \) such that \( \frac{1}{\alpha} - \frac{1}{\beta} = \frac{1}{3} \), then the sum of all possible values of \( \lambda \) is:
\( 6 \)
\( 4 \)
\( 8 \)
\( 2 \)
