new Phaleanopsis blooms have yellow tinge

[parogers51]

I'm new to the board so hello to all. I'm retired and live in Northern Virginia. For Mother's Day I was given a lovely Phaleonopsis , my first ever orchid. It has white blooms with reddish veining. It has two new blooms but what should be white, has a yellowish tinge. What am I doing wrong? I water with filtered well water and use the spray food as directed. It sits in a west facing window and the temperature is in the low 80s. Thanks for any suggestions.