Chemical burns?

Hi, was just wodneirng if any one could help me, i'm growing 21 plants out side, 11 pot of gold, and 10 swazi safari. there growing in 8 gallon pots and they are 1 month old (some where in south uk). i have been watering them once every 2 days, and slowley been adding more nutes untill i got to 1ml to every liter, every time i water them. ( bio-gro, from biobizz) i have found what i think might be a chemical burn on 2 of the plants. was wondering if ay one know if this is a chemical burn? i have enclosed a pic of the whole plant too. ( the white stuff on the leaves in insectiside)

thank for ne help,

psymin

take it easy with them chems ,they do burn if you over use them to much ..did you try flushing the plants out ? that should help a little and stay away from the chems till you see them bounce back (limit yourself) :thumbsup: