1 strain could have a multiple number of phenotypes, it means there is lots of possible variations between the multiple breeds of plant it's been crossed with. Autos are specifically more prone to have multiple phenos (different variations) because they are crossed so many times often between 3 sub types of cannabis (sativa,indica and ruderelis) if you look at a wild ruderelis plant on Google you will be surprised to see the leaves look similar to the "mystery plant"
The single bladed leaves can also come from the plant going back into its veg cycle.
Have you changed cycle, or altered anything to do with the lights/lighting?
I also feel your feeding too much N on the "mystery plant" specifically looks dark green. Your nutrients look to contain too much N for flower, only a little is needed during the start of flower they get what they need from the leaves. However I've found depending on the requirements it is good to feed an autoflower a little added N until they stop stretching. I think you have just fed a little to much. sorry for the long post, just thought I'd offer my opinion✌️🏻️
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