Calcium deficiency?

[MrDuppy]

Hello,

two days ago I discovered a few brown spots on the upper leafs of one of my Early Queens. As I'm not sure what exactly causes this problem, I want to ask you guys.
Is it a calcium deficiency, what do you think?

Medium is dirt, fertilized with Bio-Bizz (Bio-Grow, Bio-Bloom, Alga-Mic, Top-Max). Water ph: 6-6.5
BD 35. Lamp: Gavita Pro 6/750e DE Flex

Thanks for your help in advance!

 

[Amadeus Forzin]

Do you adjust the ph of your feed? When mixing biobizz it tends to mix to a ph of 5.5-5.8. Do you adjust it up to 6.5?
I used to do this when using biobizz and all my plants loomed like this about 4 weeks into flower. I threw away my ph pen, stopped adjustments and flushed at week 3 and again at week 6. Then I switched to living organic soil and stopped mixing nutrients.

 

[MrDuppy]

Thank you. I'll have to check ph again, but last time it was 6-6.5

I was using Bio Bizz for my last four grows and never had any ph issues so I was guessing it's calcium deficiency.