Auto Euforia almost finished problems

Hello there. I'm about 2-3 weeks away from finish on 2 Autoflower Euforia's

I'm growing in 5 gallon smart pots using Super Soil + FF Ocean Forest Soil. Watering using RO water with Cal/Mag added. Light is advanced platinum p300 LED.

This is only my second grow ever. First grow had the same problems. Majority of leaves ended up turning almost black and it gave my bud a weird and not appealing smell. Here's a picture of the leaves. From the Euforia.

Also didn't mention. Temps and humidity has been perfect. 67-75 F and 45% RH.

I've had this gut feeling the LED might be burning but the plants are about 18 inches from the light.

Any ideas?

Bump

Ttt