plz take a look at my babies! whats wrong with them?

ok so my plants seem fine except for these few problems, they are yellowing btw veins, sum tips curl up and some tips curl down and a few of the tips look like they are starting to burn and turn a lil crunchy, other then that they seem to be growing fine.. i have them in promix bx soil and have been using the organicare pure veg food, liqued karma, fulvex and humex. i have been keeping the ph around 6.9 they are around 5 weeks old and i need to know whats going on with em so i can fix it, if it's fixable.. i think my ph was a lil to low in the beginning of thier life. would that mess them up completely or do i have to worry about this? im trying to find my right mother plants and have already taken two clones from each to see if they are male or female. would the clones have a def. if the mothers do to? my guess is a Mg or K def. if that's it wat would be an easy way to add sum to my soil? thanks guys..

are u using nutes looks a little like nute burn what kinda lights u using and how close r they

cut down on the nutes.

could be salts build up in the soil, i would think about flushing with plain ph'd water. My plants did a similar thing and the leaf edges were curling inwards, i had a few strains and it seemed to only affect my weakest plant, they were all in the same soil bed. Flushing fixed it for me but may not be the same problem.