Ec Burn (leaves burnt around edges)

Hi, Well basicly i Havnt been growing long, im growing in coco pete and on the edges of the leaves look like they have been burnt, i looked it up and i think its to do with the ec level being to hight, so i flushed it thorugh with plain water twice and its sayin over 3.6 soo i dunno how to get my ec down do i just keep flushing with plain water or what? thanks
Bartlett

flush with plain, properly pH'd water. pH is very important

SMG