Weird markings on leaves

Do you spill water on the leaves / are they exposed to rain? This could've ended up burning the leaves. If this is not the case my main concern would be the roots - this soil is veeeery compact and cannabis roots prefer airy soil. It could be root rot or plain lack of oxygen.

U spilling nutrients onto the leaves?

1:1 for 1.5% or 1:2 for 1%., assuming 3% h2o2 purchased.

i'm not sure, but going with root-related. even if irrigating properly, looks like there's not much in the soil to help with drainage. maybe a hydrogen-peroxide drench could kill 2 birds with one stone.. knock out any microbial growth on roots if they've been too damp for too long too often, and it'll temporarily alleviate the lack of drainage by deliving o2 to the roots as it oxidizes all sorts of goodies on the way. single drench on a water-only irrigation cycle at 1-2% won't damage roots. That's just enough to kill most of anything in the way of bacteria and fungi. 3% might be better but not certain that is safe.. best to dilute 1:1 with water some easily found 3% h2o2 solution. foodgrade is probably better than the stuff for first aid but not necessary for this application. i'd still wait for a confirmation from someone else.. i am not certain. Other leaves look healthy... and, from previous questions on this plant, maybe drainage is a larger part of the cause in hindsight. (about slower growth) From the side, the internode length is great in week 6 picture. So it's not "too much light" from earlier guess. think i mentioned the soil/drainage possibility? And, it is an auto, so there is a slightly higher chance of a runt with ruderalis genes, and autos are more volatile in size just in general.. i always use "perlite" but there are several options to choose from. a 50/50 mix with your soil would improve root growth and reduce risk of root issues. You will have to water more often, though.