Cal def, heat dmg or something thierd?

[Therealzemi]

Greetings
Been having a rough time IRL, and as a result i slacked a lot with the attention to my girls. Obviously i should have reacted way sooner. If nothing else, i hope to avoid this happening again.

Info on grow

1mx1m room-600watt hps and cooltube
There is around 6-7 liters of soil in each pot. The soil is Biobizz lightmix, where i added an extra 10% perlite
Biobizz Grow, Bloom, Topmax and AlG mix. All applied acording to their feeding shedule (feeding on every watering). I live in Skandinavia where we have high quality, yet hard water. I PH it to 6,5-6,8
Foliage feeding with 1ml Alg mix/liter of demineralized water, up untill completion of week 1 of 12/12.
Strain is Bubble Kush from Royal Queen seeds. All 16 plants from clones.

Miscoloring of leafs started fairly early in flower, and i shrugged it away as heat dmg. I moved the bulp higher than ive ever had it before since week 2 of flowering. Yet this issue seams even worse than my last grow where it was closer, and just keep getting worse. So i'm thinking something else is in play. Hope you can help out
Pictures are from today, where they got their last feeding (7 full weeks in). In 3 days time i will start flushing for a 12 day period.

 

[Therealzemi]

Another couple of pics.

 

[Therealzemi]

There must be some smart people who can shred light on this

 

[MostlyMe]

I think that might be a calcium problem. Trouble is there's no way of telling whether it's a deficiency or a lockout. Given that you are well into flower, the safest option is probably to start the flush. If things stop getting worse, a single application of some Ca/Mg supplement might be helpful. At this point the damage is basically done though.

I also have hard water and kept getting the same problem. Now I use RO water and add my own Ca and Mg. Never had this problem again.

 

[Therealzemi]

Thank you for the input Most
It's not that long ago i moved to a new place. And the water here is indeed a bit harder than my previous surply. And i did not have this severe issues back in the old place, Sadly i dont have a ppm/ec meter to check it. Perhaps an idea to invest in one. To see if i should consider getting a RO system. The area i live in is ancient seabed, and there is very high lime deposites deep down. Like meters deep. Hence the hard water.