nutrient burn and flush question

Hola, all
i have a question re: ferts, overferts, burn and flushing. i am pretty sure the leaf tips are showing burn. i have done the research here and at other sites. so, here is the ???... can i flush when the soil are still wet? or should i let the soil dry as i would between waterings?
thanks in advance for the replies of experience.

if you feel you need to flush, don't wait. 3x the container size worth of water to flush..

When it doubt flush it out.

is it starting from the bottom up or the tops leaves gone like a white yellow burn at the tips

also how old what they are in how often u water also in or out and what lights and nutes u use and do u ph

rob333,
the girls are in dark now, so i can only partially answer. i am pretty sure only the top leaf tips are affected so far. the girls are approx 4 wks into 12/12. i water by combination of feeling the weight of the pot and by use of a hydrometer. i am using cfls (total of 320 to 240 watts of 2700k) the girls are LST and the canopy is very even. i am using FF nutes and
no i have not ph'd.