I find it is not usually one thing causing a problem and the same symptoms can usually be caused by many different problems. With that said, throwing a few things at you to check.
1 - The pots look a bit dry, which is probably why my fellow Canadian pointed you at reading related to watering.
2 - It’s hard to tell in a photo but your pots look a bit small for the plant size. This isn’t to say you can’t grow in small pots (ie: SoG grows) but you have to be careful about watering and nutes
3- PH could easily cause the problem - are you testing your water? Better still, are you calibrating the PH meter regularly (I learned that one the hard way). Getting the nutrients right but not pHing the water can mean the plants don’t have access to the nutrients.
4 - What nutes are you giving them? I suspect you may be giving too little or too infrequently but some symptoms mask different problems
5 - I use HPS lights so I can’t comment on the LEDs but maybe someone else can.
Good luck! Let us know how it goes.