Leaf Issue... a Little Help Please?

[coherent]

I noticed this today. Wasn't there yesterday. Growing in coco/perlite. GH Flora nutes. Plant is vegging about 4-5 weeks old. Green Crack Photo.
Under HLG Rspec 18/6. Temps and humidity nominal (70's/50's).
2.5 ml each of cal-mag, GH flora micro and GH flora gro per gal. Watered daily. r/o water. Adj to PH 6.0. PPM after mixing reads about 350-375.
Other plants doing fine. Just this one showed this on 2-3 leaves today. They have been fine with good growth no issues up until now. I replanted into larger 3 gal smart pot 2 days ago. My guess says mag deficiency, but I'm no expert. I doubled the nutes and tripped the cal-mag for todays watering/feed to see if it responds.
Any thoughts or knowledgeable input much appreciated.

 

[GNick55]

could be the roots are suffocating from being wet too long?

 

[coherent]

could be the roots are suffocating from being wet too long?

Hmm they were in solo cups in same coco/perlite mix. Never had issues in coco with daily watering before. They were not dry but definitely ready daily for water/feed when I did so, never over watered. Replanted them 2 days ago. Prob left them the solo cups a bit to long as the roots were wrapping around the solo cup inside, but healthy and white. I left everything (medium and roots) intact and re-potted in the same mix in 3 gal fabric pot. Never dried out (due to being coco and how you should water/feed) but never excessive water/feed. Others of same time frame and feeds are doing fine. Was hoping to identify issue before/in case if does affect others. It's on lower leaves near bottom of plant. Photos I can find or charts look closest to "Maganese Deficiency" but the charts I've found are kind of funky and not sure how much faith I can put into them. Actual photos I could find kind of resemble magnesium deficiency, but you can see what I can in the photo. Was hoping some wise experienced sage grower would say.."Oh, yea, I've seen that.. it's this what it is and to do grasshopper..."