(Unsure if quote will let me say what I need) I'll say it one last time to reiterate:
By "development", Leo is the only one growing as a character easily seen throughout season 3 psychologically. He's the only Turtle I can see actual growth in; though rushing the healing hands seems jarring to be a last minute resolve to the Karai plot in The Deadly Venom. Now, as for the other Turtles I"m going to point this out:
Donatello- I don't see a single development other than the love triangle fading into nonexistent. Aaron did point this out in season 2, but the last time I felt Donnie was an actual character was the rampaging Timothy in
Mutagen Man Unleashed due to him in a harsh conflict of freezing the poor sap. The majority of season 2 did give him plot, but that's my main issue here. Donnie gets a large amount of plot which I respect, but most of them go absolutely nowhere or are rushed. A big one was the retromutagen which while hinted at up to
Slash and Destroy went on the backburner, even then the passing mentions are not there. It's a prominent issue outside why Donatello is being close to a death;y brink; it's a 180 of his development. Unless they hint at more of his smarts or utilizing his character properly, I don't see growth.
Michelangelo- Oh boy here we go, the big one to me.

Mikey possesses no growth at all; while I know this version can be handled for episodic focus, I don't see growth. Mikey might not be in the same boat with horrible treatment as Raphael, but of the four brothers I honestly think he's the second worst; if not then Mikey is possibly the worst written turtle in the series.
The Croaking is all I have to say because after his growth in season 2's conclusion with
Wrath of Tiger Claw, Kuro Kabuto, Dimension X, and
Invasion all of it goes missing by this episode in season 3. He screws up for.... no reason whatsoever and rewarded when he caused the Punk Frogs to enter the farmhouse. I know for a fact Mikey wouldn't be this stupid, but why is it he's trusting of Napoleon whereas the previous episode he doesn't trust
"Mrs. O'Neil?"
I can mention many things of each time Cipes' Mikey does an awesome moment, he takes two steps back in development. No more apparent is he bad then from the crush on Renet all the way to Dumb Don. That crush was beyond atrocious, completely out of the blue and makes Mikey a love sick puppy; I couldn't stand this behavior at all in the episode because of it being sudden. When compared to Leo, Don, or even Raph's relationships, Mikey's enters left field so suddenly even as a crush. Granted, Mega Shredder and Yokai made him how I want a Michelangelo; then
Creeping Doom comes and the character falls flat again to be an idiot. When a character as comic relief does this often, I don't laugh, I facepalm at the insulting nature. So, Michelangelo might have grown in the past but each time his idiocy in the show destroys that development.
Raphael- I would have no problem with exploration if what happens are explained in context. Personally, it's a major annoyance to use one character as a scapegoat often; no more apparent is the show doing it with Raphael. Like I said, I can tolerate issues to an extent, but the exploration isn't well executed. I'm going to use comparison to both softie Raph and badass Raph in this show on the difference. Let's start with emotional Raphael:
Arguably the common example of this series is to use Spike/Slash and for good reason. Raph often interacted with the turtle to convey why Raphael has issues in the show, especially with his family. Eventually, it blossomed into Raph having to fight the monster he created who became like an attack dog; even then Raphael did show compassion when he's under guilt for what he did. Similarly it also happened with Karai's debut in
New Girl in Town during the leadership; after Michelangelo was knocked out by Snakeweed, Raph didn't keep fighting. Instead he held back with him and Donnie taking Mike back to the lair before Raph went to Leo and Karai. These examples came from the very beginning, where Raph was caring to his family even if he's driven crazy by the household.
In comparison, take a look at other relationships in the show for this character. Given we go by recent memory, take Mona Lisa as a prime example. Besides the given motivation of her similarities to Raph, why do these two have an attraction? Not only is out of character for Raph to suddenly like her even as a teen crush, Mona is similar for suddenly liking him even as a tough guy. The chemistry was rushed throughout to make Raph macho to impress a creature he just met.
As for tough guy Raph, it's downplayed often.
Cockroach Terminator shows the tough guy persona obviously to face a fear, but others include
Slash and Destroy to protect those you love, the recent
Dinosaurs Seen in Sewers with fighting Zog and even the commencing of Casey and Raph's barely utilized friendship. Compare that to now, the only macho thing done was fighting the dragons on a planet with differing abilities abnormal from Earth, such as with the moon decreasing our weight. In addition, the only cool moment was the rematch against Rocksteady with the retromutagen in
Pig and the Rhino. ("But I didn't!") I'm not asking for Raph to be a tough guy each time, but the little moments sprinkled in assist the matters on a character who never develops without limelight.