Brown spots on leaves and dark tips - boron, Calcium or other?

[Critical+]

Soil or hydro or coco: soil

Strain: Barney's Farm Amnesia Lemon

Photo or Auto: photo

plant age: 2.5-3 months - 5.5 weeks into flowering

pot size: 20l

has it been repotted? and when?: yes - 2 weeks before flowering

soil type: Biobizz light mix

nutes or additives used and how often for soil: 3 day feeding schedule: day 1 Canna terra flores - 5ml per litre; day 2 Canna PK13/14, 1.5ml per litre + Canna Bloom booster, 2ml per litre; day 3 plain water.

Air temps (max min): 39.5 / 22.9

Res temps (max min):

humidity: max - 51% (during lights on and after feed); min 22% (lights off)

lighting type and wattage (hps, led, cfl): 600w hps

Light schedule: 12/12

ph level: 6.5

[bigW]

It looks like bunch of deficiencies to me. Your ph is a bit high and that also makes them process less of the nutes from the water. I would drop the ph down to 5.8-6.0 And add extra nutes. They really look like like they 're lacking nitrogen mainly, but probably some micros too.

[MonsterEnergy]

max temp 39.5c - definitely wanna bring that down if you can pal,

[Country]

Yeah ph is to high, if you look at ph lock out chart under iron def you'll see brown spots, i cant tell beause i only see it in 1 pic, i see brown spots and the tips look burnt as if heat is to high, check the stems on the fan leaves to see if thet are weak or hollow then message back

[Country]

Also the pic of the bottom looks fine, the plant will drop a few leaves it doesn't need, it's normal from what i see, let it do its thing with that and make it a happy plant with temp adjustments, try keeping the temp in 1 place, you won't be able to but by trying you will keep it from fluctuating as much and in turn keeping the plant happy, i would drop temp and ph, i wouldn't worry about nuts till the ph is corrected, keep us updated

[bigW]

I agree , the bottom one does look fine,if it gets too crowded for some leaves to get enough light, they will do that, but still I think they look a bit too extreme for only a little bit too high ph. I believe they most likely also need a little bit extra nutes, but it's probably a good idea to do what Country suggested, correct the ph first. See if it fixes them. If not, increase nutes gradually until they look happy and nice deep green colour. You dont have an ec meter do you ? And you dont filter your water do you ? Some people don't realise if you use ro water, you need to supply extra micros or they ll look like yours.

I also agree about the temperature. Sorting that out would definitely do you good.

Nice looking grow btw. Well done and good luck. Keep us posted. I am interested to see how it goes from here.

[Critical+]

Many thanks for all the tips everyone, massively appreciated! I've put so much work into this girl I'd hate to mess her up so close to the end. Will try changing the direction of the fan tonight to push heat towards the door, and some more pH checks after the nutes have been added to the water - I use plain tap water that I sit in half open bottles for 24 hours, which could be lowering the pH. Should I keep to the feeding schedule I'm using?

[MonsterEnergy]

definitely wanna keep it as healthy as you can right now, this is when the buds start swell up,
they don't look over fed, so can feed as needed,

since it's soil the ph should sort itself out, soil buffers the ph itself,

[bigW]

If that's the case with soil, and it's not the ph issue, then they definitely need more food. I have never grown in soil so not sure how the ph works in soil, but the plants look low on nutes to me.

[MonsterEnergy]

i dunno if you have hard/soft water or what the ph is,
since you're adjusting the ph, might be to low/high so that can mess with them,
since the soil needs time to readjust it back to ph 7

every person grows there own way, so it's very subjective,
the best teacher is practice unfortunately lol

my tap ph is 6.8 and hard water, so perfect for me & soil