My girls need help!!! Can anybody plz help!!!

I HAVE A HAD BIG CHANGE IN THE PLANTS CONDTION IN THE LAST FEW DAYS, IM A NEWBIE AND THIS IS IS MY FIRST PROBLEM I HAVE COME ACROSS.
I HAVE LOOKED AND READ LOTS OF OTHER PEOPLES THREADS AND STILLL HAVENT A CLUE....
I GOT THESE CUTTINGS TWO WEEKS AGO AND THEY CAME WITH SPIDER MITE, BUT IVE SORTED THIS PROBLEM AND EVERYTHING WAS LOOKING GOOD TILL THE OTHER DAY WHEN I NOTICED MY GIRLS WAS LOOKING DOWN. I NOTICED THE TIPS ARE TURNING YELLOW AND NOW HAVE TURNED BROWN, THEY SEEM TO BE DRY AND CRISP. IVE GOT THESE UNDER A 600W HPS I KNOW ITS THE WRONG LIGHT FOR VEG BUT IT WAS TO LATE TO TRY AND GET A 400 MH BUT MY FRIEND TOLD ME THEY WOULD BE FINE AS LONG AS I KEPT THE LIGHTS UP AND DIDNT LOWER THEM.
FROM PUTTING THESE PLANTS IN THE EBB&FLOW THESE HAVE BEEN DOING OK. IVE NOT CHANGED THE NUTES OR ANYTHING DIFFERENT.
THE BUDBOX

12-14 EC

PH 6.0 BUT DID RISE TO 6.6 TILL I
KNOCKED IT DOWN

75F DAY
HUNIDITY 50%

66F NIGHT
HUNIDITY 80+ NIGHT I DONT KNOW WHY THIS IS RISING SO HIGH

LIGHT 18-6 OFF
PLZ COULD ANYBODY HELP ME SAVE THESE

from the description you have given of the leaves it sounds like nute burn

thanks whitewidow2

ive just flushed the full system with plain clean water, and filled the res with clean water, will these be in to much shock now!!
and also how many times should i 15 min flood and drain in a 12 or 24 hour cycle??????

20 views and no help!!!! somebody give me some advise so i dont lose them!!!!!!!!

its definitely nute burn...

that is a VERY high EC for new cuttings... i run that kind of EC when my girls are in heavy growth, whether its veg or bloom... those girls are too small to take a solution that strong.. it needs to be about .7 or so for the first week or so until roots develope and growth starts taking off..

its better if you need to flush to fill your res up with a 1/4 strength solution.. this will actually help flush the plant out better than plain water will... they shock shouldnt be bad... but you dont want to not give it nutes...

as far as flooding goes, 3 or 4 times a day for 15 minutes at a time should be plenty.. your girls are over watered, thats why they are a little droopy...

First thing that i would do is mix a batch of water ph it at around 5.5.After the water has been ph'ed then flush the plants till the top of the grow medium soil will look kind of frothy this is normal keep flushing till this dissapates.Leave the plants for a couple of hours in a place where the excess water can run of somewhere like a bath or sink.Once the major part of the water has been flushed out then this is the time to make a fresh batch of nutrients up ph the water after adding the nutes to the same has the flush water 5.5.5.5 is ok for plants during veg and flowering has the greenhouse seeds threads will show you and if it is good enougth for them then it is me and should be you.The next step may sound like alot of water but belive me the plants will be fine add the new made nutrients and leave for the excess to run off then re introduce to the lights.Doing this about once a fortnight will make the plants far happyer than if you only flush at the end of the grow the plants produce alot of salts and other bad things that need to be flushed out.Also make sure that you are not over watering use the finger to put down the side of the pot and if it feeels damp then wait till it is dry.That is one of the good things about doing the above the plants will only need a max of two waters a week.

thank you very much for your advice but the thing is im growing in clay pebbles not soil! ive flushed out the ebb system and res and started again with 1/4 strengh nutes and ph 5.9..
when the lights came back on ive checked up on them and seem to have picked them selfs back up again a little. so what should i do from here???????