When I've seen Mg deficiency it manifests as paler green striping rather than white.
If that's Mg def, you have had a deficiency for a long time and didn't catch it in the early stages, and your temps are contributing to the white appearance of those necrotic patches.
stinkyattic Reviewed by stinkyattic on . Yellow stripes, crispy leave, discolouration. Hi all, we have 2 plants under a 400w HPS. They are being given Bio-Bloom nutes, in the correct doses. The water is at around PH 5.5-6.5, 2 liters every 3 days. It will be 30 days into flowering tomorrow, but over the last few days the leaves are beginning to get yellow 'burn' like stripes. This is only on one plant specifically. I hope the pictures attached will show what I am talking about, any information as to what can be done to prevent more of this and what the problem is would Rating: 5