What kind of deficiency is this?

[ddw3x]

I flushed it one week ago and just added nutrients at a half recommended dosage with cal mag today. Is it a deficiency? When will I see a positive sign of recovery? And will the already affected leaves need to be cut or will they recover?

 

[LoveGrowingIt]

I flushed it one week ago and just added nutrients at a half recommended dosage with cal mag today.

Why did you flush it?

Is it a deficiency?

I'd say it's more than one. Magnesium for sure. And nitrogen, too.

When will I see a positive sign of recovery?

Probably several days to a week, if it recovers.

And will the already affected leaves need to be cut or will they recover?

Yellowed leaves won't recover. I'd leave them if they still show some green.

 

[JIMKSI64]

If you flush for a time based recommendation with no problems NO problems it is recommended to return to the feed rate that was working out.
If you flush for a lockout situation and had an active nutrition problem it is standard to reduce feed and ramp back up. The yellow and any necrotic leafs will not heal. Cull dead stuff.
If you flushed for any other reason other than a lockout nothing was fixed and the plant decline will continue.