if they're burned from over-fertilizing the last thing ya want to do is add more ferts...even if after flushing thoroughly. ferts are also stored in the tissues and roots and flushing will not affect what has been absorbed. instead of adding more ferts, give them a hefty dose of super-thrive. just hormones and plant vitamins in it, no ferts and it's excellent for shock and recovering plants. add more ferts ONLY after the plants have recovered and 'asking' for more...my experience tells me they won't need any more at this late stage. if they were in veg you'd want to add more but still only after they have fully recovered.