Help..1st indoor hydro grow..feminized Arjans Ultra Haze/Jack Flash

This is my first grow and my first time doing anything besides just using the forums for reading and research, so any advice or help would be much appreciated along the way.

Im currently growing 3 female arjan ultra haze at the moment and a bagseed unknown plant. I also have 10 jack flash feminized that just sprouted root tips and have yet to break the surface. ( my germination was 100% successful thanks to a couple inventive tricks i stumbled upon)

I am running a waterfarm 8 pack with controller( about to upgrade it for recirculation and valves), while the bagseed is in a big rockwool block(who cares about the test dumy). The room is 6.5x5x8 and we are currently using a 1000w MH, with intentions to swap it for an HPS for budding.

These are some pics of the set up so far and the seedlings..about 2 weeks old...bagseed is about 3..

those sort of translucent brown spots on the last pic are actually brusing...I was reconfiguring and spilt all the pebbles with the plant all over the floor and the pebbles did a little damage...other than those few spots the plant is fine.

I have one problem coming up....The plants look good but the very tips of the leaves are dried and brown...its weird though because the first pair of true leaves doesnt have this problem..and the margin of the top leaves seem to be curling up a bit...does anyone think they could pin point this problem? about 5 days ago the ppm got to high around 700 but I brought it back down to 200 but it seems like even new leaves tips are drying out...also a couple days before I brought their nutrient solutions PH down to a 5.3 which may be a little low?...any help would make me feel alot better...I want this to turn out to be a succesfull grow..thanks

looks a little like nute burn, flush pots, and lowwer nutes 10% to 20% walk it back up slowly.

lol yea no1 was helping me out on this thread so i made another one which iv gotten ALOT of help from...yea thanks though thats exactly what it was...it had gotten up to past 700 ppm at the stage u see them in here..way to high...i didnt have much control over ph and ppm until a little while ago when i upgraded my system to recirculate...check out my other thread though if u wanna see how theyre doing now...https://www.rollitup.org/marijuana-plant-problems/159409-help-plz-seedling-leaves-drying.html

not a problenn, glad you cought it, hope all is running good now. i was floating thru the threads, saw yours last night without an answer, so i thought i would pitch in. i dont post often, or much, but my advice comes from over 8 years growing.

yea everything is goin pretty good right now I think...they look good to me anyways and are just taking off..thanks thor