Dried out and brown/grey leaf tips. Grey-ish and purple leaves and stems.

Hi all! First of all, this is my first post and I have to say I love this forum!

Ok, I do have a problem with my plants.
After two days of flowering I have gotten some sick looking leafs.
Some of the older leafs at the bottom of the plant, are drying up and turning grey/brown.
It starts at the tip and edges of the leaf. Check pics.

A lot of the older growth also has a purple tint to them. Mainly on the outer edges of the leaf.
The color is very dull and matte. Is this normal?

The stems are also turning purple. Mainly the upper side of the fan leaf stems.

I fed the plants with EC1.2 the day before starting flowering.
Thought the dried up leaf tips might have been nute-burn, so flushed the plants until runoff showed EC of 0.20 and PH 6.4.
The runoff before flushing was EC 2.00 and PH 5.8 (low, right?)

As I am using BioBizz Light Mix, which has an EC of 1.2, I did not feed the plants after repotting, until now.
I have given the plants B-52 and Voodoo Juice, following AN's recommendations at 1/2 strength trough veg.

And yeah, one of the plants has light-burn. Grew too fast for me. Fixed it by bondaging the plant a bit.

Specs
Strain: Bag seeds (I know, but it's my first grow).
Grow medium: BioBizz Light Mix (PH 6.2, EC 1.2 from bag).
Pots: 11L (2.9 Gallon).

Watering: When needed, usually every 3-4 days.
Nutrients: Advanced Nutrients PH Perfect Grow, Micro, Bloom (Hobbyist level package).

Grow box: W: 2ft L: 2ft H: 3ft.
Light: 250W CFL, Warm White 2700K
Ventilation: Intake and exhaust, changing air every 2 minutes. Carbon filter on exhaust.

Temp: 22-26C (72-79F)
Humidity: 55-65%

maybe just a tiny bit of overfert, and maybe a little damage due to pH flux

this guy ^^^^ is right on bro , a wee bit of stress sort the p h , water etc and you'll be brand new . your plants look the dogs bollocks m8 i would look at the watering schedule.. every 3/4 days is a bit sparse imho

phos lock-out, secondary to above stated over fert. EC and PPM have no place in soil growing. imo

jofey said:

this guy ^^^^ is right on bro , a wee bit of stress sort the p h , water etc and you'll be brand new . your plants look the dogs bollocks m8 i would look at the watering schedule.. every 3/4 days is a bit sparse imho

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Thanks for the reply!
I am really happy about the bushyness.. I've done no training/trimming..

I've been waiting until the 2" top inches is dry before watering.. as Ed Rosenthal recommends in his book. But I'll try a bit more. Never got any signs of overwatering. Maybe I'm just too carefull

scroglodyte said:

phos lock-out, secondary to above stated over fert. EC and PPM have no place in soil growing. imo

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Thanks man!

That's kind of what i figured. So flushed the soil with PH7.5 water. Eventually got the PH up to 6.4. Damn.. it took over 12 gallons of water to get there.
Any tips for an easier way to up the PH?

If EC/PPM has no place in soil growing.. how do I know how much to feed it? Besides feeding when you obviously have a def?
Just asking, I'm a newbie.