Near harvest....what is this?

I’m 5 weeks into harvest on these autos does anyone know what this is just for future reference on next grow thanks

low calcium would be my guess. Could be ph lockout too. Have you checked ph?

Gorillabilly said:

low calcium would be my guess. Could be ph lockout too. Have you checked ph?

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Runoff ph his 6.3 I use ro water but I use calmag every time