First of all, Welcome to the forum and to raw feeding
I've got a few comments and suggestions that may help out.
The first is that having a kitten gain that much weight from 4 months -9 months (assuming my math is correct
) isn't all that concerning - compared to if an adult cat had the same sort of weight gain. She may just be growing up to be a big kitty. Without quite a few other pictures I can't say for sure, but in general kittens are eating because they need the food and will either run it off or go through a growth spurt anyways. Basically, I wouldn't worry about Cleo being overweight.
Secondly, for your picky princess Aglet (I've got one of those too
) You may need to teach her that it's food. It sounds like she was pretty solidly on one food as a kitten, and unfortunately in adult cats that generally translates into 'pickyness'. Basically she didn't try many things as a baby so now she's convinced only certain smells mean 'food'. I'm curious about what you mean when you say she has pica...but I think that's a topic for another thread.
A good way to convince Aglet to eat the new stuff is edible is to break some of her dry food down into a powder-like consistency (food processors and hammers work equally well for this task) and sprinkle a bit on her portion of the re-hydrated raw. Step one either way is to start feeding her kibble in meals at the least. Leave it out for 10-15 minutes then remove the bowl. She'll catch on pretty quickly and it'll give you a better chance of switching her to the raw if she's not grazing.
I'm not sure if you need to keep the Stella & Chewy's in the freezer...but I've never used it so just to be safe follow the indications on the bag. I've never seen it in the freezer section of the stores that carry it locally, but the bags are still sealed there so *shrugs*.
As for whether it's 'real' raw or not...IMO it's a stepping stone. Like the raw-food version of a gateway drug. Because it's more processed than your average raw food you will be missing out on some of the benefits (chewing and breaking down meat is mentally satisfying for cats, chewing raw bones cleans their teeth, ect), but it can also be more convenient than some of the other options out there.
If you're interested in going to less processed raw food there's lots of info here on that, if you and the kitties are happy with Stella & Chewey's well then that's cool too.