big bud probems.. help please

Hi fellow growers, ive a problem with one of my big bud plants and its starting on one more slowly. its the common claw in the leaves but this time im a bit stuck on what is causing it this time, ive spoke to the local grow shop about it and had a bit of input but now i think its time for some other experience growers take on this problem..

3rd week of flower
flood and drain hydro system
ionic nutes EC 1.8
ph 6.2
temps 85
clay pebbles medium
plant= big bud
h2o2 every 3-4 days just below recommended dose

it seems to be more on the bud sites than the fan leaves but it is on a few of the fan leaves, i thought maybe the roots where sitting in a puddle of water so ive put something in the bottom lifting them out (and all the rest are fine(plants))
the grow shop lads suggested maybe under watering so ive put the flooding up 5 minutes, which at the moment light on at 7 am first feed 7.30.. second 12pm.. 3rd 6 pm..
they were flooded 15 mins at a time
any suggestions would be very welcome! thanks for looking and sorry for poor quality pics, needed to take some quickly

I thinking its over watering more than under watering
When their droop is cause by lack of water the leaves laid flat straight down almost
Over watering gives you the claw look

take pics with the lights off

looks like they are asking for water.. 3 to 4 day in between waterings with clay pebbles medium seems a bit long.

hi thanks for the replys, they get watered 3 times in one day.. ive been told maybe its because the water in the reservoir maybe to warm and that over 20c they may struggle to take in, i checked the temp and it was 25c so maybe this? thanks for looking guys