The bet has, I would suggest, been settled incorrectly. You have been given odds of 1.832 to 1 for Rose and 3.168 to 1 for Mickleson. Neither of these makes any sense when considered against the odds of 14-1 and 22-1 that you were quoted.
As a minimum, at one fifth the win odds you should have received £23.00. This is calculated as:
£2.50 @ 14/5 = £9.50
£2.50 @ 22/5 =£13.50)
At one quarter odds you should have received £27.50. This is calculated as:
£2.50 @ 14/4 (7/2) = £11.25
£2.50 @ 22/4 (11/2) = £16.25
Both your selections were placed (they finished joint second with nobody else) so there should be no reduction in the odds.