Brown spots on autos. Halfway thru week 5. Also, stretching rlly bad, under same conditions

The ocean forest should be good for 4-8 weeks on its own. I see you only recently began feeding, so that's good. But, cal mag each week ... if that is necessary i'd stop buying OF. Plus, got your own super soil portion too. too many unknowns to be certain. How much was added.. how much was already there etc... A few things on leaf chart look to fit including Mg deficiency which could be locked out from too much Ca.... i'd lay off the calmag for a bit, personally. See if it is lockout. This is least invasive path... before guessing on adding stuff. always easier to add.. taking away is a bitch. The conflicting symptoms makes me think lockout is cause not a deficiency. with a hot soil like OF, you'd want to wait for plant to ask for nutrients. then with that familiarity, jump the gun around that time in future grows. OF is not 100% consistent either, so still good to see a visual queue first until you are more familiar. Also before any majore reaction, are you watering properly? wait for top 1 inch to dry, then fully saturate.. a little runoff helps ensure you don't leeave any dry pockets which can raise hell with pH and nutrient concentrations. since you ahve a super soil component, i'm a bit hesitant to say get a good 10-15% runoff, like you would in a soilless substrate. that will merely strip away your substrates baked-in nutrients. But, do make sure the whole thing gets hydrated.. whatever runoff it takes to be sure of that. if that sounds different, i'd also do that for 7-10 days before major changes to feeding. Assuming it doesn't take a nose dive, of course. i wouldn't top autoflowers too often... in addition to them being on a "timer" the stress could cause that time to go off early and cause a reduced yield. if it is growing like you say, no worries this time. In future, try finding something to use as a riser for the shorter plant... = even canopy.