New Grower Yellowing/Lightening of Leaves. Is this an Mg deficiency?

[Kazman420]

Problem: Yellowing/Lightening of Leaves. Slight upwards curling of serrated edges on select leaves. (With a touch of browning on one fan leaf)

Medium/grow method: 70/30 Coco/Perlite. (It's a Canna Brick but I washed and buffered it myself this time. Low and behold, no gnats!)

Feed and Supplements: GH Flora Series 6-Part + Hydroguard + Recharge (1x week). [+Yucca as a surfactant] 5.8 pH @ 550ppm (.5 Scale). I just got my automatic drip system in place a few days ago, so I'm now able to do some high frequency fertigation. Previously I was hand watering 2x a day.

Water source: Tap + Ascorbic Acid (~55ppm, .5 Scale)

Strain/Age: Mephisto 3 Bears - Day 54

Light used: 400w HPS (MH for Veg). 20/4 @ 50 DLI / 700 PPFD

Climate: 55% RH, 75 Room, 73 Leaf. (67 w/Lights Off)

Additional info: First noticed about a week ago, but I forgot how much HPS bulbs cover up problems. Initially I thought this was a clear case of a Magnesium deficiency but now I'm not so sure. It's worse than I thought it was. @Mañ'O'Green wisely suggested I make a post here in the infirmary. Hopefully it's early enough to correct any issues.

I had a nitrogen toxicity about 3 weeks ago and some of the larger/older fan leaf tips never completely straightened out, but all the new grow has been fine for a while now.

Pictures: One pictures are a little dark so I brought down a portable light to help with the rest. The issue is that I cannot move the plants now that they are hooked up to the automatic drip system and I have a really large reflector hood. It's casting a massive shadow right over the top of the plant. If needs be I can bring in more lights. Let me know.

This first image is the worst of all the effected leaves...

 

[Kazman420]

Just realized I should have included more details/info about the nutes I'm using. I'm following the schedule below (reduced to 550 ppm) and am in Bloom Week 4 right now.

NPK's of Micro, Gro, Bloom:

NPK's of CaliMagic, Floralicious Plus, KoolBloom:

 

[Mañ'O'Green]

Looks to me like you are still getting too much nitrogen? The leaf burn is P-K-Mg lock out. I would do a good 50% flush of 30% strength nutrients with a little extra Cal-mag + iron for the coco. Then resume using week 6 schedule at 600 PPM. Try to get less N.

 

[Kazman420]

Looks to me like you are still getting too much nitrogen? The leaf burn is P-K-Mg lock out. I would do a good 50% flush of 30% strength nutrients with a little extra Cal-mag + iron for the coco. Then resume using week 6 schedule at 600 PPM. Try to get less N.

Hey @Mañ'O'Green, thank you for replying!

Could I trouble you to clarify this; "50% flush of 30% strength nutrients". Do you mean fertigate with 1.5 gallons (3 gallon pot) of 30% strength nutrients (180ppm)? Or am I totally misunderstanding you? (Sorry I'm really stoned, right now.. lol)

 

[Mañ'O'Green]

Hey @Mañ'O'Green, thank you for replying!

Could I trouble you to clarify this; "50% flush of 30% strength nutrients". Do you mean fertigate with 1.5 gallons (3 gallon pot) of 30% strength nutrients (180ppm)? Or am I totally misunderstanding you? (Sorry I'm really stoned, right now.. lol)

That is exactly correct. You don't want to flush with just PH water. that puts a lot of stress on the plants. Even the 180 PPM will be stressful but we need to get that coco back in balance and that is best done from a low baseline. Then just start fertigating with the lower N week 6 schedule as soon as you would normally fertigate. It is easy to go back if the plants start to look hungry. I doubt that will happen.

 

[Kazman420]

That is exactly correct. You don't want to flush with just PH water. that puts a lot of stress on the plants. Even the 180 PPM will be stressful but we need to get that coco back in balance and that is best done from a low baseline. Then just start fertigating with the lower N week 6 schedule as soon as you would normally fertigate. It is easy to go back if the plants start to look hungry. I doubt that will happen.

Thanks @Mañ'O'Green! I just finished flushing her as per your instructions. I'll keep a close eye on her and report back in a few days.

I really appreciate the help.