Different leaf parts from same strain

So...I have two plants. One gave me trouble and I thought it was going to die. After two months, it suddenly started growing. During those two months, I started the second plant. The one on the left is about 2.5 months old and the one on the right is about 3.5 weeks old. The strange thing is, even though they are supposed to be the same strain, one is HUGE and the other is small and the leaf parts are different. As you can see, one has 5, total and the other has 9. Is this normal? Is it a mutation?

As the plants mature the number of fingers on the leaves can increase. Your larger more developed plant has more fingers on the leaves. It's normal, not a mutation.

Structure can vary among “ same strain “ plantings , even from the same seed batch . Breeders often push out F1 or S1 generations and that can lead to different looking plants sometimes or plants that are feed sensitive , etc.

Pheno variations happen , part of clone hunting for some growers.

They look good btw.

Thanks, guys! I'm hoping to have better luck. To date, I've never gotten past the start of flowering (tiny little buds). First plant was in soil. I lost it to flies, so I switched to DWC. Lost the second plant, in the DWC, to root rot (temp was WAY to high for hydro), started a second one and it wasn't growing at all so switched back to soil. The smaller plant, on the left, is the one I moved from the DWC. I thought it was dead but, after a month, it suddenly started to grow. The one on the right, the bigger one, has been soil the whole way through. So far so good.

Now...because I've never gotten a successful grow...I have no idea what I'm doing, once I get past the flowering stage. Hopefully I can get all the info and advice I need from you guys? Seems like an amazing place for information! Any starting advice for a complete noob?