Is this nutrient burn?

Worm Castings will never burn your plants unless you add a bunch of stuff to the castings. Just a heads up about worm castings. Always assume a problem like this is due to pH. My troubleshooting sequence for plants goes like so: 1- check pH of run-off 2- check pH of Water 3- smell soil and check roots if you can to make sure there's no root rot or problems 4- stick your finger as far as you can into the soil to check moisture 5- check underside of leaves for pests 6- check light distance and intensity 7- Check relative humidity 8- Check temperature This path usually tells me what I need to know by the time I get to step 8. I hope it helps.

That was through a massive ph fluctuation. Your ph was well outa wack and it got effected. It won't repair itself so just keep your eye on un effected leaves to make sure you sorted out the ph properly.