Yeah a pump up sprayer litterly 1 or 2 pumps and get under the leaves aswell mate
the over nute possibly stressed her enough to allow infection , i had the same but i underfed

its a right balanceing act isnt it bud
If you can get some Biowetter , i would mate its worth it , remove infected leaves 5 mm down from infection on blades and keep treating .
also have a look at your environment and see if any improvements can be made to air exchange, even shortning any extract ducting even 1m will give better air flow out, keep bends to a minimum , little things like this can all help to keep lsf at bay matey ,
hope this helps mate , good luck
stickyrussian