Bought a high nitrogen plant food 10.5-2-2

Just fed my poor baby (followed manufacturers instructions mixed 16 drops of liquid feed with one litre of spring water, did not give her the whole litre) she was quite dry anyway.

Fed her sister with just spring water with a ph of 6.8, her sister is in same conditions, same soil everything and is doing great, I am confused.

How long will nitrogen take to improve yellowing? Because if no improvement it has to be magnesium, doesn't it? Will use Epsom Salts if yellowing don't improve. It is a process of elimination until I find the cause and cure it.

PLEASE PLEASE PLEASE help with brown stripe problem? I am thinking it might be genetic, I can't find anything like on the web or on here.