chronic leaf turning yellow/white then drop

using canna pro+ soil, 10%-15% added clay pebbles for increased drainage/aeration
indoor
handwatered, as and when needed, 1 to 3 litres each daily
using mainly rainwater (fresh) ph comes in @6.9
vegged for 3 weeks, flowering for 5 weeks (day 34)
advanced nutrients of canada nutes,
gmb ratio 1-.5-1 ( yes i do the micro less because its too strong when added equal ratio, the previous plants had overdose of micro, and i still has this problem)
additives : sensizyme,fulvic acid, humic acid, big bud (week 2-5, overdrive 6-7, bud blood week 1)
ppm, starting e.c 1.0 upto 1.7 (week 5-6) lowered to 1.0 week 8
2x600w 60/40 sylvania hps sodium
day temp@23-26 night temp20-22
humidity, not measured but guessed @ 40-50%
12/12
200mm air intake 200mm air outake
grow room size 2mx1.5m


ok now ive got the specs out the way, time to describe in best words possible my problem. im growing chronic. the fan leaves are yellowing, turning white and dropping off, 2 out the three plants are extremely pale, the soil was all mixed together, so rule that out or all 3 would have symptoms.
the nutes, all fed together, same amount, same times,
position in grow room, the plants are rotated, cant be hot spots or cold draughts
now the pale plants, grow and bud like fuck, by day 45-50 even the buds will be yellowing slightly, i leave until about day 55 when i have to pull them over concerns the tiny leaves in the bud are dying and will cause mould.
the healthy darker plant looks indica dominant, more compact, darker green foliage, suffers little leaf drop until the last week (week 9)
the paler plant are more swayed to sativa i presume, larger less dense buds, more of a "spreading plant" than compact one.
i have grown these clones in dwc, and soil now three times, and cannot seem to correct this problem, (oh the seeds yielded two phenos, hence the darker green indica dominant and paler sativa? types).
i am bit of a novice growing "large plants" i might be completely wrong and this be normal?
my last attempt yielded about 6-8oz per plant, they was tiny compared to these monsters lol
can i foliar feed something earlier on to slow the leaf drop? any suggestions be welcome, thanks, ill attach a couple of pics for viewing shortly.

i thought id add, the pot size is 30 litre, i forgot to mention it i think.
ive tried looking but with no success on this yet, are indica dominated strains more tolerant to latent heat? the grow room temps fine ... i was wondering about the latent heat of the plant leaf itself, you see its the leaf that would be doing the most synthesis that seems to be the ones most affected.

Indica's are mostly darker green because they come from desert like area's. sativa's can take the heat but are lighter green. sounds like your doing things right but they should look more like the darker green. Towards the end of a plants life it is natural for the leaves to yellow but not the whole plant. They look good just on the light green side.

They look like they have been flushed for a long time at the end of life cycle or a nute lockout. When a plant is flushed it starts like eating the green out of the leaves. Anyway they look good enough to smoke for me.