Few questions about canna coco nutrients? Has anyone used them that can answer these questions pleas

Would much appreciate anyone's input who grows successfully in coco with canna nutes..as I'm having some problems..

1. When do you start using canna coco nutrients when growing in coco? As I started at about day 7( 2nd set of serated leaves) started only using 2ml per litre an giving each plant in 3 gallon pots about 250-300ml and feeding nutes daily..they was fine for the first week..then i upped it to 3.5ml still at 300ml per plant then a few days later started getting severe an rapid spreading nute burn..instead of flushing I'n one sitting I gave them 500ml plain water everyday and they still continued to get worse..so I resulted in flushing an after 2 days they picked up new growth was fine but now I've started them back at 2ml per litre A+B But the plants are bigger so they've been getting 500ml..but now they're droopy all the time.. and light brown rust patches/spots on the tips of each top leaves..although I'm sure that its a cal and mag Def cause i had one with my 1st grow..but also realy quickly the tips of random leaves are appearing to be clawed..an yeah I'm sure it's nitrogen toxicity but it's confusing me why it's happening on that amount which are loads bigger..and doing a feed,water,Feed an I'm going by canna hard water-light feed aswel here's a pic at there worst.. and then now..they have still been growing but still droopy an kicks like the nute burn is slowly coming back..I just don't understand I'm hardly using any nutes as it is?

Plain water in a coco grow is a no no. If you feel you're over fertilizing cut back on your percentages, but don't cut back to nothing. Also, I don't use Canna nutrients, but looking at their site, they recommend mixing the nutrients in order; be sure you're following the directions. And while it's hard to tell by your pictures, being they're under some sort of yellow light, I would say for starters, you need to get a handle on your pH. Lastly, clawed leaves are not 100% correlated to a Nitrogen toxicity, so don't be misled. If you are indeed feeding as light as you suggest I doubt you're at a toxic N level. Pictures under white light would help.

Did you get a handle on things?