Not sure what deficiency this is

It's 18 days into flowering , I am using mammoth p , mega crop 9-6-17 , recharge and farm fox chapel ching 9-50-10. A lot of the top and middle leaves are becoming yellow . The pH of water is 6.54 and it is in a potting mix soil with 15% perlite . The humidity is 54 and the temperature is 73f . IMG_20190414_190122.jpg IMG_20190414_185918.jpg IMG_20190414_185931.jpg IMG_20190414_185918.jpg
 
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