Some folks just can't get away from the "More is better" mindset.its nute burn, im no genious to figure that out, you gave them way too much fert for such young plants. they shouldnt even need ANY nutes if your grow medium is 1/2 way decent should provide them with all they need.
learn to follow directions shitty fert or not, flush them and start over without any nutes till 6 in tall then just give 1/2 of recomended dosage.
you probally just set yourself back 2 weeks ODing your plants, right now you should be lettign thier root system develope so you can transplant them into thier final grow container without worrying about stressing them out