Why are my autos so tiny, while my regular plants are thriving?

[highacutance]

This is my third year growing, but first time with autoflowers. In early February I popped a lot of beans, both auto and photo. I'll be transplanting the photos outside in late May, and by that time I expected a nice harvest from the autoflowers. Strange thing is, the autoflowers are tiny and the photoperiods are at least twice the size. These are grown under LEDs, 18/6, in super soil (Coast of Maine Stonington Blend). I do check the pH of the water, but otherwise nothing added. Strains are LSD-25 (photo 1) and Tangiematic from 42FastBuds. Note the blue ball point pen for scale. Nice frosty top bud, (photo 2) but I'm guessing 1/4 oz yield. Finally, note how the photoperiod plant, Mass Medicals' Putang, towers over the Tangiematic auto. Same lights, same soil. I also grew some autoflower Anvil by Mendalarian Genetics. The first five out of ten seeds were male, 8" tall males. I'm growing the rest of the Anvil seeds now, hoping the remaining seeds are all female. I'm beginning to think the autoflower revolution is a lot of hype. Three different seeds from two different breeders, and the plants are tiny, where under the exact same conditions, the photoperiod plants are thriving.
Comments?

 

[Edinburgh]

Yea heres the drill fast buds are my least fav auto breeder, if there beans arnt germanateing or the flower is fluff, i have had there plants dwarf out on me, here is a pic of gorrilla glue by fast buds, if your gonna run autos stick with Methisto or Sweet. So pic is gorrilla glue by fast buds that dwarfted out on me, look familiar?

 

[Moshmen]

I won’t order 420 fastbuds again , IMO just unstable genes. Don’t count out the autos from o d bad experience, they are great for exactly what you were trying to do! Try some different genetics next time. I consistently pull 2-3 zips from autos in 2 gallon pots
What you usin for light?

 

[highacutance]

Edinburgh, sad to say, I'd be happy with that yield compared to what I'm getting. Lighting: I had several Viparspectar "full spectrum" LEDs which were supplemented this season with HLG 360 units. The Vipars use the blurple and white LEDs. The HLGs look like golden sunshine in comparison. Another issue with this grow has been that the organic super soil isn't quite cutting it. Look closely at the big plant in the first photo. You'll see some yellowing along the edges of large leaves. Some say LEDs can lead to Cal Mag deficiency, which is what that looks like. I guess Mephisto is good. That's why they're always sold out!