flush again ASAP ,use 3 x's amount of plant pots ie; 11 litre pots then flush with 33 litres of water etc............you wont cure the nute burn but only stop it,leaves will die but wait till 50%+ damaged before taking off dead leaves.
4 weeks old , what amounts of nutes you been using,i know your using water now but what amount of feed & how often did you feed them?
reason i ask is your soil should have enough npk in it so you should not need to feed any nutrients for at least 3-4 weeks....
the good news is they look healthy enough & with being in veggie stage a little selective pruning,get your feeding schedule right & your away bud
