Rusty spots 43 days (9 wk auto)

Hi, second grow and having rusty spots on older leaves in an otherwise healthy looking plant.
Fox farm HF and OF mix (3 to 1) soil grow plus a little perlite in fabric pot.
Almost no nutes added except in week 4/5 in half recommended strength of fox farm trio. Added some microbes as well at wk 5.
Runoff ph is always low since started under or around 6. So, have been using tap water (7.4 ph) for watering. Tried not to have too much runoff as I added no nutrients. And started foliar feed cal mag when i first noticed the spots in wk 6.
Mild temp within range. Low humidity under 50 most of the time (so cal weather).
Take it outside for sunlight half of the time. No pest on leaves I can see.
Is it calcium deficiency? Thought they happen more on new leaves..?
Any help is appreciated.

Looks like early cal deficiency

Didnt notice in your post that you are running 7.4 ph … that is out of range for plant and medium.

Bring that to 6.5-6.7 only. ( ffof is 6.3 out if bag ).
Tap is fine but keep it close to recommended so buffers in soil can do its job better.

PLUS …. Stop runoff checks.
Totally unnecessary. Everytime you run excess water thru medium - you unbalance it by LEACHING. Keep it simple. Keep ph in check and let soil do the work.

Thanks! I tried not to have runoff this time around. Last grow was a disaster following FF nute schedule (even at 50%). I am not intensionally having runoff. Will ph it lower when watering.

Auto breeder times are always off anticipate three weeks more

I think it is similar issue with this white widow I have? Same environment as the auto above, but I did add 50% nutes at wk 4/5 and have been using small amounts of nute for ph’ing my watering. Am I not supposed to do that? Runoff ph was at 5.6 every time. I flushed at the end of week five, but issues worsen at wk 6. Then I though higher ph watering will correct it, but it doesn’t work as you mentioned above. I did throw some lime on top in wk 5 when the issue first surfaced.
Question - should I eradicate the issue first before I switch? I want to switch it today if tmr…

thx again!

First of all
taking it in an out is making nearly impossible to diagnose your issues for me

Plants like a steady environment ...KISS

Oh, thought the plants like natural sunlights everyday! I did keep it indoor since week 5 as I started scrog.
Could the change in environment stressed it?