No coco wash = mg Deficiency?

I am currently using %50 Roots Organic and %50 coco fiber. This is my first time growing in anything other than hydro so i didn't realize that i am supposed to flush the coco before use. I did ph the water and added sensizyme to is before i mixed it with the coco. I am now into the 2nd week of flowering and it appears as though i have a MG deficiency (lower leaves(ones beneath the canopy) have intervienal chlorosis, some are dropping and there are random light brown spots on some of the upper leaves. I have also noticed a few necrotic spots on some of the lower leaves that are falling off. I am currently using AN 2 part with most of the AN line (Bud candy, bud factor x, Nirvana, big bud, sensizyme, F1, H2, and barracade.) All of my plants ( half sour diesel, half AK 47) are receiving the same nutrient mix but about 1/7 of them are showing signs of deficiencys. My questions are:
1) Is this a result of me not rinsing the coco?
2) what should i do about it? I was thinking of flushing the affected plants maby with a light cal mag solution.
3) am i screwed? I know it is hard to answer this with out pics (ill post tonight when lights come on) but i have read that mg defeciency can lockout other nutes and ruin an entire grow.

Thanks for the help and sorry for the long post but i wanted to include as much info as possible.

1.)Maybe
2.)Yes, thats ok
3.)No

haha your getting repped for making me laugh. So i just did a runoff test today and I found that the PH is too high in my grow medium. I put in water at 5.95 ph and it came out from 6.0 to 6.69 with the majority of it being between 6.3 and 6.6. Correct me if i am wrong because as i mentioned before this is my first soil grow.

1) A PH that is too high means too much lime in the medium?
2)What is the best way to lower the ph of soil? Can i simply water with plain water at 5.9 or say 5.8 untill it adjusts?
3) Should i use a product such as clearex seeing as i cannot just use 3x the volume of my grow medium worth of water ( I have 150 gallons of grow medium in a scrog setup so i cant exactly use 450 gallons of water to flush.


Thanks for the help guys. I did soil this time because it is supposed to be more forgiving but this is getting tough. Flushing ect. cmon man if this was hydro i would just nute swap and done. This will be my last soil grow.

Wow if you using that much soil the fastest way is to get some sulfur to counter act the lime. With just pure water it will take an intire grow to lower the sulfur will lower it a lot faster also if your still in veg try to turn in some peatmoss it has a pH of about 4-5 and will lower the soil down to around 6.5 with what i have gathered so far. Clearx may help but is usually just to get rid of nutes. lime is tuffer because it breaks down over time.

I flushed today with 11 cups of water per 5 gallon bucket with light cal mag phed at 5.85. There was about 4 cups of runoff and it seemed as though the runoff has lowered in ph between .2 and .4 so now i am in the right ballpark i think. The highest runoff was at 6.49. Tomorrow i think i will reflush with a gallon of 5.9 water for each 5 gallon and see what that. If i have holes in my buckets do i have to worry about overwatering them?

pix help much more. do you have red stems higher up the plant?

I know you're using quite a lot of stuff, but what does your EC come out at after measuring the nutes?