Help somthing wrong with my plant

hello guys few days ago i noticed one of the leafs dried and died and i ignored it
Now my l plant having more like it what can i do it looks like the whole plant having a hard time
It is 6 weeks old on pre flowering
Auto
Water it every 3 days ph 6.8 nothing unusual
Pls help

is it just that 1 leaf? could u take more pics? from the other leafs in the background the plants looks ok, it looks like a burn from touching a light maybe?