First timer trying to diagnose disease

This is my first time growing and i am having some problems fixing what i think may be an Mg deffiency.

I have a bubble ponic system that i bought from stealth hydro that houses five White Russians that were grown from clone. I use the nuits that they gave me but do not give the plants the full dosage. I usually have the ph around 5.5 but after reading on a few of these forums I increased the ph to slightly above 6. I have also been foliar feeding them with a 2% Epson salt mix. These plants are having the most trouble.(dscf1052)

I also have four plants in a home made hydro set up with the same factors as the last one 2 of the plants are runts and barley growing while the other 2 are growing the fastest in the garden, but they all have this discoloring. (dscf1046)

There are also 5 plants in soil. There are 2 Hindu Kush plants that are about a month older than the rest of the plants they are doing great and show no sign of discoloration, the 2 White Russians that were cloned at the same time as the hydro and seem to be growing very well too. There is another clone of either a romulin or Cali mist(dscf103), I am not entirely sure, that was doing great but is quickly going downhill. All of the soil plants are given the recommended feedings of fox farm nuits.

I first saw some discolorization about three weeks about and I tried to flush the plants out but it did not seem to work so the past 3 watering have been with water and Epson salt only.

I have included a few pictures, please help me to figure out what’s going wrong.

https://www.rollitup.org/view.php?pg=faq&cmd=article&id=588
mos def looks like Mg deficiency. at ph 5.5, little is available. is it possible the ph wen't lower? were you slackin? i'd guess it's ph fluctuation/Mg combo. the dead leaves are long gone; cut 'em off. as long as you keep it okay now, the plants should recover. maybe you should cut out the salt, eh?

ok sounds good, thank you for the help.

How sick should the leaves be before i need to cut them off or should i cut of any sick leaves?

first off clean your room, wipe everything down with a product from advanced nutes thats meant to control all surfaces of the room. then take a close look underneath your leaves and inspect carefully. look for little webs. i think i see little white dots on the tops of your leaves, this is called stipling. spider mites eat directly blow the little white spots.then either spray the underneath of your plants with safers endall or neem oil if you want to go to a hydroponic store but safers is everywhere .