Leaves rusting and curling - HELP!!

Hey guys - 3 weeks into flower and started noticing rusty patches on leaves + some curling up.

Can anyone advice what deficiency this is if it is a deficiency?

• Strain - Amnesia autoflower
• Temperature = 23c, humidity = 50%
• In soil, feeding quarter strength biobizz organic grow and bloom nutes
• Light is 12-inches above cannopy
• LST and defoliation up till 1-week of flower

Any help appreciated!

What light is 12” above canopy? That is either a weak light or it’s too close. Looks like you have a calcium def. and Mag def.

i dont see a light 12" above the canopy

Think it’s the angle I’ve taken the pic at. The light is a Mars Hydro TSW2000 led light. Will take some more pics showing the angle. And will feed some calmag, hoping that helps!

Looks like a soil PH problem.