Thanks for the replies again, all insights welcome
last night I scooped out a few litres of the solution and put some plain water in and got the ppm down to about 850, they should be pretty big now at around 3 weeks but still only 10 inches tall, the burnt tips must mean over fert so I will see how they get on with lower ppm.
I also did the same on the White widows which are only about 1 week in and were starting to show the first signs of nute burn so I got them down to about 600.
These numbers still sound high but check the canna calculator at http://www.canna-uk.com/growguide and it's what this recommends!
last night I scooped out a few litres of the solution and put some plain water in and got the ppm down to about 850, they should be pretty big now at around 3 weeks but still only 10 inches tall, the burnt tips must mean over fert so I will see how they get on with lower ppm.
I also did the same on the White widows which are only about 1 week in and were starting to show the first signs of nute burn so I got them down to about 600.
These numbers still sound high but check the canna calculator at http://www.canna-uk.com/growguide and it's what this recommends!