Plant troubles

Ok guys your probably saying anouther newbie with yellow leaves and you would b right but this time the yellow leaves r near the top I use biobizz all mix and BB grow and bloom the girles r 6weeks in and I have only just switched to 12/12 2days ago.i have been giving them 3ml per ltr water as recmd of grow so assumed that it is not lack of nitro.dont no wot to do any help v welcome ( c pics)also I topped one of the girles and although she has good hight she seems to b a lot skinnier than the outhers.i have 4b cheese and 2 sleestack/skunk 1

pic 1 shows some burnt tips....sure sign of over-nutes.

also the colour does not look great, first reaction was cal-mag def but I'm second guessing that it could be bugs/mites but hard to tell from a single pic...pic 2 & 3 provide no value as the HPS alters the colours too much

burnt tips and yellow leaves.... could be nute lockout, maybe try flushing the soil, or the ph could be off. then again, i know nothing....

hard to tell from pics but imo from pic 1 i would hit it with cal/mag the next watering and then flowering nutes 1/2 strength the watering after that. this may also help with the purple stems.

if you already fed flowering nutes then i would do cal.mag next watering and plain water the next after that.

Don't want this to sound daft but I can't get onto my hydro shop for the next 2 weeks (going on holiday tomorrow)can I get cal/mag at my local garden centre.if not wot else can I use.

Third pic is the plant I topped.y has it gone so skinny?

Greenhouse save...you say you're using 3ml per litre...should be 1ml in BB all mix