leaves turning yellow with dark spots over some leaves

hi guys can anyone HELP,please i know very little about these plants at the moment,as i have put them on here for a friend who is actually on holiday, the very little informtion he said to mention, is they are grown in soil ( canna tera profesional soil ) was given terra vega up untill week and half ago, when he changed light to 12/12,, he then started givin them terra flora,they are in betwen 5 an 6 wks old and are under a 400 hps light (3 plants), he gives them flora every couple of days when they need it he says,( about a ltr and half / to 2ltr )the temp is kept in between 75/80. They where like this before he went, (5 days ago ) but i believe they have gotten slightly worst, so thats the reason he have asked me to put them on here, hoping someone will recognise the problem, Sorry for the litte information guys, if theres any thing you need to no, then please ask, as he will e mail the answers to me, "thank you all in advance" Just been told that the water havent been ph,d ,it was just left 24hrs , he was told by the guy in grow shop, that there was no need if growing in soil,he also added that he hadnt seen any signs of growing "in the week before he went" and he believe they are jacks,CAN SOMEONE TELL ME IF I SHOULD CUT AWAY THE AFFECTED LEAVES, or should i leave alone, thanks

I don't know the exact cause of your problem but I do know proper PH is important. I always ph my water whether I'm feeding them or not.

It looks like a possible phosphate problem, if plant are not over watered i would say ph aswell causing nute lock out. New here not trying to play the expert just trying to help.

Im going thru the same ordeal and was told it could be nute lock out or toxicity. Could be watering too often too. I was told to let them sit til the soil is almost pulled away from the edges of the pot before watering again. And if that dont solve the problem then the other alternative was to flush the shit out of them. Hope it all works out for you. Seems to be a nice looking plant otherwise.

thanks guys for ur answers, will forward all messages on to him