Did the Pink Oyster reader not reduce the rate correctly?

Yesterday I traveled from Hayes & Harlington to Tooting Broadway Avoiding zone 1 and pressing the pink reader in West Brompton. The Oyster card is linked to a 16-25 Railcard and the entire trip was off the top. However, it charged £ 1.80 instead of £ 1.00 (price of the traveler's unique price) is this a mistake or have I done something wrong on the trip?enter the description of the image hereenter the description of the image here