Asking some writers/artists I follow:
Is there anything in your fic/comic that you as the author know about, but won't end up in the actual story?
This is a great question! I'm gonna try to answer it without spoilers.
Though ERICA is focused on Raph having Hanahaki, I have been thinking about how the others would deal with it, and what might cause it.
For Leo, it could come from a number of things, just because I imagine that he would bury many of his stronger feelings for the sake of "being a good leader." I've already said in the fic that he knows Hanakotoba (Japanese language of flowers), so he would probably figure out what his flowers mean and confront those feelings on his own, before anyone could even realize he had it. That being said, his primary flower would be a blue balloon flower (yes, I'm colour-coding them), because it's the Hamato clan symbol, and ultimately he's suppressing his emotions for the clan.
[I'm also a bit obsessed with symbolism of it in Tale of the Yokai and Owari so I thought it'd be fun to use for one of the turtles]
I haven't given much though to how Donnie would get Hanahaki, but the first thing that comes to mind is disagreeing with Leo or the others (like end of season 2/Don Vizioso type of arguing). When Donnie thinks he's right, he will think so until explicitly proven wrong, so I could see him quite literally dying on a hill of his own pride (or coming really close to it). Hydrangeas would be kinda perfect for this, because they can mean pride and arrogance, but also apology and understanding. Donnie might know deep down that the others are right, but he doesn't always want to admit it.
With Mikey, I can think of two major causes, but I'm gonna focus on the more likely one: suppressing his childishness. Mikey's inner self is canonically a 6 year old kid in a world of imagination, so if something were to happen that would forcefully make him "grow up" (mayhaps Splinter's death), or he takes his brothers' words about being too immature to heart, the disease would come down on him like an anvil. In this case, his flower would be freesia, and I like to think the colours would become duller the longer it lasts (really emphasize the loss of innocence/vibrancy metaphor). I don't think he would try to hide it from his brothers for long though, if they don't discover it on their own. Mikey's probably the most willing out of all of them to actually talk through his issues.
I haven't thought of anything for April, Casey, Karai, etc, but I did decide that Casey has had Hanahaki in the past. There was going to be a scene of him talking to Raph about it, offering advice on how to cope until he's ready to share his feelings, but I cut it when I couldn't fit it in organically (I might still write it separately tho).
I've also been compiling what's essentially a medical doc for how my version of Hanahaki works (causes, diagnosis, treatment, etc). Some of it comes up in the fic, but I might still make a detailed post about it in the future just because I've put a fair amount of research into it.
[Sorry that this got kinda long, but I hope you like reading it :)
