ebb & flow yellow/brown tips

Hi All!

I was hoping there was a quick answer for this while the problem is minor
tent data:
PH 5.6, EC 1.06, & res temp 62F
air temp 75-79F @ 40-50% humidity
400w cooled hood 10+ inches from foliage

Currently all the plants on the table are starting to yellow/brown at the tips on the older lower leaves and moving up, they are flooded 4 times a day in 12/12. I know that the pump runs for 15min and starts draining right before the light comes on and the table is still flooded when the light turns off.
Could watering in the darkness cause this problem? Its becoming a real pain in the ass to fine tune these analog timers, when the power goes out or I replace my res water its awful to get them synced again.

A couple days ago I noticed the problem and consulted "the bible". My res was a bit low and I hadnt really increased my EC value in a while which was .860 so I added another 5gallons and brought the EC to 1.050 with AN micro and bloom

It has been a couple of days and the problem seems to be worsening
here are a couple pics, sry there from an iphone that wont focus on a small object

What are you using for medium? If you are using rockwool....you should only flood once a day as the rockwool retains large amounts of liquid. It is possible they are getting over watered or the strength of the nutes is too high. Not all strains can handle same nute concentration. I once had a strain that wouldnt grow and was yellowing and browning, unless using plain old tap water.

i flood 4 times daily for 3 mins, just enough for the water to rise 3/4 up my hydroton then flood straight back out. The quicker the better apparently. Flooding for 15 is basically drowning the roots. the roots will find exactly the same nutes in all those balls. if your in wool, can u add balls to your system or are they potted?

With my attention to detail i forgot to mention my medium...
I am using hydroton, I started the clones on the table in rockwool plugs and after they were well rooted into the hydroton i tore the rockwool off carefully and seated the plants. Before i got to the rockwool on the older plants they started to form algae so most of the table now has a green tint to it. From my understanding this should not have any adverse effect on the plants growth.

I am unable to flood the table for anything less than 15min, both analog timers that i have are 15min intervals.
there are 2 different strains on the table TSS and BBxAK both are showing the same signs.

Would this be a magnesium deficiency? I was informed to use 1/2 tea spoon of epsom salt per gallon of water. Will this have any adverse effect on the plants if it is not a mag def?

So i am still unsure of what to do. I am using RO water with advanced nutrients 3 part G-M-B, do you think its a micro nutrient problem?
In the beginning i was adding superthrive but since its at a friends house currently i havent added it the last 2 res changes.
I have also been warned not to use it on late flowering plants but if the water is filtered through a RO it has been stripped of nearly all nutrients.

Please get back to me, Epsom salt or Superthrive!?!?