Deficiency or nute burn? SOS

Hi RIU community,
first sorry for my poor english .....

I need some advise about the issue I am facing now..(Again!, and I am getting crazy can't figure)

Quick specs:
Veg 18/6
DWC 5g bucket using 2,5/3g
RO water
1ml oxyboost
Lucas formula micro / bloom 1:2 ratio
at 400 ppm at the moment or 0,8 ec
Ph in range with hanna meter 5.7 / 5.8 the meter is new and I double check with the ph drops.
now she is under a 240w backstar with a cfl 50w
temp rez 17/19max

Sorry, I forget to take a shot of the roots. I can do it if needed.
I was thinking a Mag def or a nute lockout. she was at 500ppm but it seems to get worse so down to 400.
I really want to figure what the hell is going on because it happened in the pasts grows and I can't fix it
Pics:

Hope someone can help!
Thanks for your time.

Looks like u burned it

pretty low EC for nute burn on a plant that large, but I agree.. it looks like burn to me too.

Perhaps there is something wrong with your meter?

dannyboy602 said:

Looks like u burned it

Click to expand...

woow ok I was thinking I was way to low .. first time using lucas ...
so I put the ppm to 300 ppm ..let's see!

BossHoggins said:

pretty low EC for nute burn on a plant that large, but I agree.. it looks like burn to me too.

Perhaps there is something wrong with your meter?

Click to expand...

thanks to confirm.
I will lower Ec and check what's up with my meter. but If I have 8 micro and 16 bloom diluted in 3 galones it gives me about 350 , I am at 1/3 strength . full strength is 1000 so my meter can't be very out. can it ?