Slow growth yellowing leafs at bottom...

Hi, I am growing in coco/with some perlite. The plants are from seed and allready 1.5 months old
but they been growing very badly ,slow growth with constant yellowing leafs at the bottom which looked at some point like nute burn, which might be that I used recycled coco which probably had some finishing PK residue in it (I didnt really flush the previous growth)...so I have flushed with rgular water these plants (I might need to do again ,if it aint working) 2-3 weeks ago..
now this is a totally new location with well water which has an EC reading of 0.7 straight from the pipe..
I have done cal mag foliar, which didnt really help , and now I have been doing Nitrogen foliar spray (whit some Nitrozyme from Growth Technology) daily, some of the other plants looked to get better from it...but these are not looking like they are getting any better...the total EC with fertilizer has been 1.8 so 1-1.1 of fertz + the 0.7 from water---
I am using Canna Coco range.....what should I do is there a lock out or whats going on....
the yellowing leafs have been curled up and dying + falling of on their own so it indicates nitrogen deficiency...
maybe these actually have the magnesium def but then at least the leafs and branches should been spreading out ,now the growth is tight and small leafs ,not branching out and really slow growth...

Looks like too much P too early to me...

Never cared for Coco..... I'm sure there's some one here that may reuse their Coco..... I might be a bit uncomfortable doing so but, like I said. Never really been a fan of Coco.

Same old problem, it had been a long time from the previous usage of the left over coco so I totally had forget that it was not flushed
and of course containing all the PK which I used at the end of last growth....so I let the pots dry a bit and do an other flush properly and then back with low amount of nutrients after 3 days of drying out from the water only apply...of course the leafs will start to yellow even some more because lack of nutrients but they can't go on like this either....and I am bit uneasy of just adding more nitrogen to the tank...the foliar way has usually been the safest way of correcting but since they are not really responding well to anything its time to do a rinse...thanks DR Who, we can always count on your knowledge