5.9 in soil is too low, somewhere arond 6.4 would be better.
Yes, food.... at this stage of flowering, they will need a "bloom" type of fertilerzer, not a "grow" as your diary shows.
Basically, she is hungry for potassium and phosphorous.
Looks like the plant can't absorb calcium and magnesium due to the wrong pH value in the soil. I'm having the same problem right now. The pH value should be between 6.3 and 6.8.
Looks like a potassium deficiency by the discoloration and spotting. Flowering npk ratio is 1-2-3. That , or if you are growing in coco then it could also be ph issue in coco.