ec confusion

Hey guys , iv got a sensi northern lights and 2 white widow x bigbud vegging verticle around a 250 w mh , in 5litre (1.2 gal ) coco , they are getting fed twice a day now as they have a very solid root base and they are pretty big for there pots , being fed h&g coco a+b a touch of cal mag and canna rhizo,
The strage bit is the plants are thriving at 340ppm (0.45 ec) And if I go up to 450ppm the leaf tips start to build up to much nitrogen , does this seem strange ? Is my metre maybe way out of calibration? It seems like a really low nutrient dose ,
Im mixing 10L of water with 6ml of a
6ml of b
0.75 of cal mag
And 6ml of rhizo
And tapwater with ppm of 70
Does this sound a out right ?
Iv had plenty of nitrogen toxitcity in the past so just trying to figure out whats going on , cheers in advance for any ideas or help

The additional calmag will be adding some N to the mix. It could also be causing a lock out by throwing out the Ca N K relationships. I'd expect the H&G nutes to be fine without additional calmag, though I've not used it. Where is your pH at with your feeds? Leaves can vary a fair bit in shade, pics would help too

Yep I dropped the cal mag as its prob not necessary, iv switched to canna , iv had problems with h&g in flower before but most likely was due to serious humidity and heat issues ,
They are all sorted now but I like the way canna stays at the same ph for days so im sticking with it