yellowing/browing grow problem 4 week since seed.

I'm 4 weeks from seed.
I'm using 66% Ocean Forrest, 33% light warrior.

I started using a seed tray, then transplanted into light warrior at about 7 days. About a week after that, I noticed yellowing on the bottom leaves. What I didn't know is that light warrior provides no nutrients, and so I did a 1/2 strength nute using fox farms, but within 24 hours just decided my best bet was to repot into 66% Ocean Forrest, 33% light warrior, as OF should have enough nutes to last a couple of weeks (or so I thought)

The plants seemed to take well to that, but the existing yellowing got worse, which I expected. Those leafs dropped.
Now, the yellowing has suddenly came back, and worse it is now effecting the one plant that previously showed no sysmtpoms.

The plants are under a 400W in a cool tube. The temperature at the canopy is a max of 78 degrees, and around 70-72 degrees during the dark cycle.

I water every 48-50 hours--whenever the cups feel almost as light as a solo cup of dry medium. I'm using distilled water and the PH is right around 6.5.

I've done one 30% strength nute since the yellowing showed up on the previously unaffected plant. The yellowing/browning continues, all on the lowest (largest) set of leafs.

Any guidance would be great. I don't want to put in nutes if the soil is already too hot.

I have always done bydro but letting the medium dry out completely tends to destroy new roots and the hairs on the roots. The problem could be the ability to absorb nutrients and not a lack of nutes in the soil. When I first messed around with growing I didn't let the dirt completely dry. just dry for the first inch or so with good drainage. OF should have water retaining stuff too. So maybe don't let it dry so much. Also a lot of strains tend to like higher 70's temps when veging. But make sure humidity is over 30% or the plant will sweat more than it can drink.. especially if the roots are dried. All I can think of.

check these out and see if you can find your answer there, Im new to growing so only know what Ive read and learned first hand these seem to have pretty good info with
pictures...
http://www.cannaversity.com/cannaversity/article.php?id=057

http://www.growweedeasy.com/marijuana-symptoms

http://www.weedguru.com/forum/viewtopic.php?f=88&t=27907

The first leaves(3 fingered) normally die around this time it's normal but if it progresses to other leaves it would be a problem,so don't add anything out of the normal or it will create a problem that wont go away (leaf damage)

HotShot7414 said:

The first leaves(3 fingered) normally die around this time it's normal but if it progresses to other leaves it would be a problem,so don't add anything out of the normal or it will create a problem that wont go away (leaf damage)

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What a relief! Just goes to show how much of a newbie I am. I'll keep doing what I'm doing, because everything else seems to be going well.

It seems to be spreading to the next set of leaves (5 fingered). I have No idea what I'm doing wrong.