Mg Deficiency ?

3 weeks into flowering.
Most bottom leaves have yellowed and fallen off.
Some middle leaves look like the picture.Others look yellower(?) but greener in the veins of the leaves.
Some top leaves appear dry and brown near the tips that are curling upward.
Is this plant Magnesium deficient?
Nutes: I give 5ml DNF Bloom part a & b to 2 liters water every 2nd watering & 1 tablespoon blackstrap molasses to 4 litres water in between nutes.

Looks like a PH problem. Are you giving any nitrogen for flowering period? I generally give a very small does every 3rd watering. I also get some micro nutrient fertilizer and use about a tsp every other watering. Im leaning towards micro-nutrients or PH.

could be that your over fertalizing and/or not flushing your medium enough

Looks like what I have and I have MG deficiency. Flush now before it gets really bad, then feed with cal mag or add some epsom salts. Has your ph gotten down below 5.5 for even 1 day?

I don't have a PH tester. I don't think it can be a PH prob because I don't give it much nutes. I think I should have continued to give it veg nutes until the second week of 12/12 instead of right away switching to bloom nutes. I gave it some cal/mag today and will see what happens.What is perplexing is that out of 4 plants ( 3 x chronic & 1 x strawberry cough) x only the chronic have this prob. the SC is doing just fine.

When I use flowering, organic nutes, it drops the PH like crazy.

The water will have a PH of 6.8, and then when I add, 1 tbsp of fert, and it drops to 4.0 or lower. It all depends on what fertilizer you use, but it will change drastically when you add ferts. With a PH of 4.0, your plant will not be getting the nutes it needs. But again, its just a guess.

That could be your answer right there. Strain. If you're feeding them all on the same regimen, its possible the SC requires less of the veg nutes to continue to thrive (or they haven't begun to show signs yet, so you might keep an eye on them).

...you need to get a pH meter...flush your plants, catch your runoff and keep flushing until you get your pH in range (6.0 -6.5 for soil/less)...after flush, add you some cal./mag.

...good luck.