I tend to agree with Roberts, however, I have removed some leaves incase of septoria but I suspect my airflow, humidity etc is sufficient that septoria shouldn't be an issue.
Reading more into both P & K def I'm going to up my feed and see what happens, as per Roberts's suggestion.
Growinggrannie, If I wasn't so sure about my conditions (I was suffering with low humidity) appreciate your input and will certainly monitor the situation carefully.