Hint: The fourth player is the key to this tricky question.
Answer: 9 points.
Respectively the scores were 7, 14, 20, 30, 23, 9.
If the six player were A, B, C, D, E and F we know that:
A + B + C + D + E + F = 103 
A = B ÷ 2
B = C - 6
C = D x 2 ÷ 3
E = D - A (see note at end)
F = E - 14
Since D is the letter we're missing information for, it's best to find all of the other letters in terms of D. These steps are left as an exercise, but the result is:
A = (2D - 18) ÷ 6
B = (2D - 18) ÷ 3
C = 2D ÷ 3
E = (2D + 9) ÷ 3
F = (2D - 33) ÷ 3
We can then use these all in  to find that D = 30. Which allows us to find F = 9.
Small note: if we chose E = A - D (instead of E = D - A) we'd end up with a negative value for E, which isn't allowed.