Autoflower

I second redbeardgrows comment on checking your mediums PH level. I had a similar problem with a blueberry auto that I'm currently growing, my waters PH was always between 6.2 to 6.5 but my mediums PH was literally 5.2 to 5.6 in all 4 of my plants (in soil) I got myself some crushed limestone, and within 2 days I noticed them all come back to health quickly, its been 4 days now and they look healthier than ever so I'm sure when I recheck my PH itll be back up where it should be. Mine only began flowering a week ago and they are now 7.5 weeks old. Looking very good for your first grow mate, this is my first indoor grow but I've had several outdoor. Looking forward to seeing you harvest . As the other guy mentioned, adding some cal-mag wouldnt hurt either, I add it to all my nutrient solutions now just to be safer and keep them healthier :) (I got a mag deficiency, but turns out it was from nutrition lockout due to low ph) Happy growing!

have you checked your medium's PH? I saw in a video dude was having a similar problem and it turned out the soil PH was up around 7.5 even tho he'd been watering 6.0-6.5. Hope they get better soon bud!

I would say you have high temperature and humidity in the tent. Try to reduce it. I might as well reduce nutrients and try to add them cal mag.