Thanks for the advice. I'll look into the Tri part nutes.
Any experience with the biobizz nutes?
Yes, I was using the green house powder feeds. Never had an issue with burn on any of my photoperiod plants. Also, I don't think they burnt my autoflowers, they were just really stunted so I'm assuming that I might have been a little heavy handed with the nutes. I know there are a plethora of other reasons for a stunted plant, but I have to start somewhere.
Having said that I've never used any other nutes to keen to try experimenting with other methods.