(HELP) LED Coco grow leaves yellowing

Hi everyone new to the forum!
Need help with my current grow.

First of all my set up:
Grow tent 80x80x160
300w Mars Hydro LED Grow light
4x 9 Litre air pots with catch trays
4inch aluminium ducting into 6 inch carbon filter and 4 inch extraction fan. Have this running during the plants night cycle to cool tent down and for extraction of stale air.
45w greenhouse tube heater for heat as the LED doesn't produce very much. I also have an oscillating desk fan inside the tent for air circulation.

The plants themselves:
4 x super silver haze by expert seeds
Germinated using paper towel method and placed straight into coco coir professional plus growing medium in small 2.5 inch pots where they grew under 2x15w CFL Bulbs to about 3 inches in height with 2 sets of small leaves when they were then moved to the larger pots.


Nutrients
For first part of the grow I used no nutes only tap water left at room temperature and ph of 5.8.
Up until they moved to the bigger pots where I then began the addition of the canna products.
For the first week in the new pots I watered once with 1.6ml of Canna A+B in 1 litre of water spread between the 4 pots. 5 days later I done the same except 2 litres of water between the 4. 5 days later I flushed with normal water and returned 3 days later and topped up with 3.0ml of each canna A+B and 2ml of Cannazym.

My problem now resides in the fact that since moved to the big pots they have exhibited yellowing at the tips of the leaves turning into brown then dying. I cannot make sense of it as I must be doing something wrong. This happened to my last set of white widow in the exact same setting and regime as this grow, they subsequently all lost leaves and died bar one which is now growing on my brothers windowsill and is happily developing new leaves since placed in a smaller pot with different premix soil.

Forgot to mention the plants are on timer for 18hrs on 6 hrs off and the heater stays on all the time bringing the temp of the tent to about 24 degrees celcius in the day and 19 at night.
Any help very much appreciated I'm advance. Happy growing to all.

 

The brand of coco is Cannas own brand 'Coco professional plus' as seen below.

I didn't precharge the coco but did flush it before plant use to get rid of any excess salts. I don't understand what you mean by buffered (still learning )

I had personally thought that I should have left them for longer in the smaller pots but they were getting rootbound in the small 2.5inch pots and i had no medium sized pots to transfer to, nor did I have the space as they were touching the bulbs in the space I was using to start the seedlings so unfortunately had to be moved some way read online about adding perlite to the mix, am definitely trying that next time.

Didn't realise that the light was too small for the space, if you had the option of what to do in terms of light would you buy another mars hydro the same size and have the two? Or would be better off changing to a HPS/MH type lighting setup?

Thanks to everyone for the quick replies already I really appreciate it. Every day is a learning day!

 

Thanks very much for the help, your babies look so healthy, buds look beautiful! I never realised THAT is what root-bound looks like out of the pot, mine certainly had more life in them in the smaller pots, lesson learned!

That's the exact reason I went for the smaller LED that I did as I was a bit worried about extraction, heat and fresh air circulation. What light are you using yourself? Would love to eventually get to a point where I'm getting yields close to your own!

 

Wow I am very impressed, quantum boards hard to put together? I'm an engineer so I suppose nothing I couldn't learn how to do! Seems to be the most cost effective and as per your pics, beautiful yields.

 

Cool man again really great info I'm definitely going to look into those thanks for everything!

Been a busy morning this morning took the babies out, trimmed dead tips, carefully removed from the 9L pots and lifted each seedlings and root package out of the pots, rinsed very softly under warn Ph5.9 water and replanted in smaller pots again in same mix but flushed with same 5.9 ph water, no nutes, going to flush for 2 days I think and then begin to add nutes at a much lower dose than what I was, wait for them to hopefully recover and grow some more roots and fill those pots a bit, then I will look into potting in bigger pots once they've matured a little bit. As for ppm, I understand that means parts per million but how do people measure ppm? Do I require an EC Meter?



I feel she's definitely going to get crowded in there with 4 plants, gives me an excuse to start a new project maybe for a veg tent/ clones as that's something I would definitely love to learn more about after I master some of these coco growing basics! I think the easiest option was always to go with a more beginner friendly growing medium but I wanted a challenge ( I certainly got that ). Let's hope for the best!