What do you look for to determine hi/low Nitrogen?

I have checked the stickies and got some info, but nothing matches quite what I need to know.

First off info:
Growing in foxfarm OF under 400 watt hps lamps ( 6 of them ) in a 8 x 8 flower room

What I need to know is what are the 'signs' of over feeding? I am aware that underfeeding is characterized by a light green or greenish yellow tint to the fan leaves, at least that is what I have read so far.

What I am seeing on my fan leaves is a yellowing on the ends of the 'sawtooth' part of the leaves. Is this caused by over feeding or under feeding? The leaves are a healthy green so I assume it is not underfeeding. I may be wrong on that though. What are the FIRST signs of over feeding that you look for?

I'm trying to learn to read my plants, but I guess I'm pretty illiterate in my plant reading and am a bit confused on this.

No pictures, sorry, camera is loaned out at the moment.

I appreciate any help that you can give to clear this up for me, thanks in advance.

pics are equivalent to about 4 paragraphs, ahha...but i believe "nute burn" generally starts at the leaf tips..

excessive nitrogen causes mutations in my experience, low nitrogen causes yellowing and will stunt growth.

Ocean forest rarely has a nitrogen deficiency unless you've done something very strange to the soil.

Too much almost dark green/blue and clawing.
Too little gradual yellowing until leaf drops. Starts at the lower ones.
pH, too wet, burn, low K can get the sawtooth areas.

Nute burn cooks the tips first. Done it.

I have never seena nitrogen burn. I just always see super blue and seriously mutated twisted leaves.

So the yellowing on the sawtooth areas is not high N but low K ? Its just on a few plants and maybe I'm over reacting.
So Too high of N = blueish tint and twisted leaves, and burnt tips.
and Low N = yellowing on lower leaves.

Its not that I havent done my research, its just that there is so much contradictory info out there. It also seems that I can never find what I specifically need to know. Especially when it comes to Nutriants and mj.
Thats why I use the forums, because I want to get feedback from people who actually grow and know their stuff.

Thanks folks, I appreciate you taking your time on this

is this what you mean by yellowing in the sawtooth part?

lord ganja said:

View attachment 2472910 is this what you mean by yellowing in the sawtooth part?

Click to expand...

Yes but just the very tips and not spreading to the rest of the leave.
Thanks

If its just the tips its nuteburn. You can flush and give 1/4 strength nutes to fix

lord ganja said:

If its just the tips its nuteburn. You can flush and give 1/4 strength nutes to fix

Click to expand...

Thanks a LOT. Believe me when I say I apreciate an honest straightforward answer to my question. I did flush yesterday and we shall see what the results are.
Again, thank you.

Looks like Mg to me.

This is what helped me

http://m.youtube.com/watch?v=-_IM7XEcxgw