Is a flushing in need?

So I have 3 Northern Lights about 2 weeks into flowering, I have been having overfeeding problems from early start, before i really knew the importance of the less is more mantra. Every time I add water without nutrients, signs of excess nitrogen and nute burn sets in, tips turn yellow etc.

Should I flush my soil?

Some will say yes, some will say no.

So far, they seem to do be doing fine overall, I cant see them as having too much salt buildup as I have only added a few waterings with nutrient solution from the beginning. BTW I am using FFOF soil.

Its just that after a few days they show signs of needing water and as soon as water is added bits of nutrient burn start to show especially in the new leaves.