Led at 18" ....
Watch how much nitro she is getting ( flowering ) ... ( red stems , dark green color ).
Sounds like you are on a 12/12 with this auto ... Which is a less productive cycle.
( smaller size , less branching )
AUTOS are wired for as much light as you can throw at them .... 18/6 typical thru harvest.
Spots look like thrips ... Check your soil for little bugs crawling around ( tiny winged ) . Thrips are also VERY SMALL worm like bugs that puncture plant tissue. They make squiggle marks on leaves. Autos are kinda tempermental ... One screw up and they go sideways easily.