Progressing problem- yellowing

Hi guys and gals! Well, this grow has definitely had its ups and downs. After a catastrophic accident where my lamp lens broke and sheered one plant in half, and took out some side shoots on the others, everything was back on track. However, over the last week, one plant has been progressively getting yellow and developing splotches on the leaves. It I've thought of N deficiency, Magnesium def, ph problems, etc., but have not diagnosed or treated as of yet. I wanted to get a few opinions first. I am currently testing pH every day, and it is a little below 7. Here are some pics, and the specs I have currently:

pH: we will say 6.7
soil: Ocean Forest
Nutes: Technaflora Organics (veg mixture)
Feeding schedule: Every 3 days: Feed, plain water, plain water, feed
Lighting: 400W MH
Temps: 79F ave. with highs at 82F and lows at 73F
Age: 7 weeks
Humidity: Running humidifier at average of 48%, but ranges from 40%-60%

If I am missing anything, let me know and I will provide you with the info. Thanks in advance for any insight and advice. It is greatly appreciated!

Sprayed with Jurassic Acid and fed with the watering tonight. We will see how it is in the morning. Oh, and the light schedule is 24/7. Any help out there would be appreciated. Thanks again in advance.

It sounds like you have most of your bases covered ... I would consider a good flushing and letting them dry up a bit before starting any nutes again . Overall your plants look pretty healthy in the pics - and it could just be natural sluffing from lack of lighting under there . From what I can see - all the newgrowth looks very healthy . I wouldnt get to worried just yet tbh ... I would just see where they go from here to see if it is a problem comming on for now

Good looking grow btw : good luck

The first thing I would look closely at is PH.
FFOF in my experience has a tendency to lower my PH by as much as 1.5points!
When I first started, I would water with 6.5PH water and my plants looked very unhealthy.
Then I measured the run-off and discovered that this soil dramatically lowers PH.
Now I water with 8PH and my plants look healthy. The other thing I read is that FFOF needs Cal-Mag nutes.

Ok, kinda looks like your leaves may be touching your soil... try cutting a half inch line down a cd and sticking it around the bottom of your stem so the leaves touch the cd instead of the soil. May be the soil is to "hot" for actually touching the leaves but fine for the plants.