"Dan, did you write 'Nanase's clothes become oversized after growing' before figuring out why that would happen?"
It's entirely 100% possible that's what happened.
"So you basically just had 'put technobabble here' written in the script for a while."
That would be correct, yes. Just like the professionals on Star Trek: The Next Generation!
And you've got to hand it to me, it does make sense. Humans are mostly water, which is incompressible, and are all sorts of complicated and weird. Clothing is fabric with all this open space and junk. I mean, yes, magic, but the less bending of reality magic has to do, the easier it's bound to be, right?
"Okay, yes, it's decent logic, but what if you hadn't thought of that by the time you got to this comic?"
Then I'd say a wizard did it.