CANNASIM answered grow question 5 years ago What's up, Brazil-radish, bele? Welcome! I already had this same problem is very boring to correct, take a look at my journal of NL, to get an idea of how it evolves, the important thing is not to remove the affected leaves, despite the aspect I got the best result in terms of harvesting. No doubt you are having problems in the absorption of minerals, I see calcium and magnesium as others have said, but to diagnose correctly I would like to suggest some measures and give other tips to avoid this.
I would suggest to you:
A/RUNOFF - take a look at the PH of the runoff, if I've been too acidic and high PPM or EC are salts present in the problem substrate or overfert. If you don't have the meter, you have simple strips that sell in the growshops, it costs very cheap, and important to regulate the PH of all irrigations to about 6.5.
B/a tip I give you if you have access is to give some product with beneficial bacteria with mycorrhizae, I use Recharge which has several types and advise a lot. It is really worth taking a look and testing, basically avoids this type of absorption problem and roots in a superior way, PH and locks coming from nutrients.
C/Another maneuver I would try if you did the tests I mentioned in point A and were positive, it would be a Flush, and finally give a supplement of Calcium and Magnesium, as correctly quoted, before.
D/ Take a look at the watering practices too, wait for the substrate to be dry testing with your finger to the second flange, and feeling the weight of the vessel to avoid excess or lack. The tissue vessels help a lot in this regard, and accelerate the growth of the plant. 15l works very well for the record.
I hope for sure, and if you need anything, I'm here. Abs and good luck with everything!