Bottom Leaves Yellowing and Many Other Problems(I Think)

[Cannabinoid]

Hi
Firstly, thanks for any help you can provide.
My Equipment and Environment
Seed: Dinafem Sour Diesel Autoflower
Day: 39
Feeding: Master TANG's Easy Auto Schedule
Soil : Biobizz Light Mix
Light: MarsHydro Epistar 160
Room Temp: Lights On;25-27C
Lights Off:19-21C
RH: %40-55

I'm using Sensi Cal/Mg every watering.(0,75ml per L)

I think she's a pretty girl but last 3-4 day i've noticed some problems. First problem is bottom leaves yellowing. As a result of research, i said, it must be N deficieny. Increased sensi bloom A+B 2ml per L to 3ml per L but this time, i've noticed leaf tips turning brown.I decided decrease to 2ml other watering. Today, i saw other problems. Brown spots on the leaf surface and twisting leaf tips. I didn't notice slow growing problem but I'm worrying about the bud development. She went to bloom phase about day 25.
I add a few photos.

 

[Discretepete2676]

Gosh I'm not quite sue on this one really. ...looks great except those few bottom leaves and a couple spots, are u really careful when you water as to not splash a lot? Also is there anyway you could do close ups of the spots outside of the tent? Sometimes hard in pics under the LED to determine what's going on. @Renaissance Redneck @Waira any thoughts? Wish I could help more myself but I'm kind of new still

 

[Waira]

hey bud! :smoking:...do me a favor, and shoot me some close-up pics of the affected leaves in better, natural lighting; LED spec' is lousy for diagnostics, and color rendition is important to analyze the symptoms,... also, despite all the hype about self adjusting pH, keeping an eye on the actual in-soil pH is wise,..plenty can go wrong, overwhelming what buffering is available; best choice for this is a soil pH probe, like the Accurate 8, meantime, the other option is the run-off method, which I generally dislike because it's prone to measurement errors,... here's a link to an improved method (https://www.autoflower.org/threads/...-testing-and-ph-estimation.41733/#post-928975)...When defc.'s appear, it's important to determine if it's being caused by a general lack-of, or a pH lock-out situation; in the case of the latter, adding more stuff in will make matters worse, not better!.... I see some leaf droop-- did she get dry, or a really heavy watering? ...burned tips like that are usually a sign of overfert'ing,...

 

[Cannabinoid]

Hi again
Sorry for the LED Light pictures, I add new photos. I haven't got a high quality ph meter so I can not make accurate measurements. But I'm using 7.4 ph drinking water.
I'm suspicious about my Honeywell Turbo Fan. Clip Fan broken so i'm using honeywell turbo but i can't attached it anywhere so i placed to floor. Fan was blowing air bottom leaves directly on speed 1. 2 days ago, i turned up it. Could this be one of the problems?
Also she has purple stems.
I'm watering daily in small amounts.(nowadays 750ml) I decide according to pot weight. In the mornings, generally, she drank all the water is going.
For now she looks normal but I am very concerned about bud development. I hope, I can find a solution.
/: Thanks for all answers.

 

[Waira]

..better, thanks! Okay, lower leaves are just getting tapped out for their store nutes, N in particular,...which is normal at this stage; the spots, and other symptoms look like some early Ca-Mg defc. starting, so get going on full strength dosing of that--also, typical at this stage!.... as for the fan, not an factor here for current issues-- as long as it isn't blasting the plant (and pot) directly, it'll be okay for now,... keep it positioned for good overall air movement, but not buffeting the plant around,... buds look fine to me, it's still early, so keep on the schedule,.. does it include a high PK bud booster? That would be a good thing to add, beyond what the bloom nutes provide...