Please Help!! Yellow Brown Leaves

Hello I am a newbie this is my first hydro dwc grow. Everything was going great then my lower leaves started getting yellow and brown leaves. I believe its a Nitrogen deficiency. I am using GH flora trio, so I assume to just up the flora micro I'm giving them since that has nitrogen and calcium in it. Does that sound correct?
Reservoir at 73 grow room at 85 RH at 44 ph at 5.8 EC is 1.5. Plants have been in system 2.5 weeks. I have attached a pic. Any help would be appreciated. Can this be fixed or will I lodse them?

When I see green veins with light striping on the leaves my mind goes instant to mg. Did you say your reservoir water is 73F? hmm, frozen water bottles.. The plants look something, wind blown, too hot, too low of humidity.. At work this computer sucks I always tell people I can't see too goodz when I'm at work, get a second opinion

I have a chiller so I can get the water temp down no problem. Everything I have read says humidity is ok 40-70. what is mg?

Magnesium