Things worth remembering:
All Stede knows about Ed's breakdown is that it was because of him (You broke him/he took my leg cos I mentioned your name), He doesn't know about Ed's other trauma aside from his dad and while he knows Ed is disillusioned with pirating, he doesn't know the specifics about why.
Ed tends to speak in metaphors and while Stede tries to understand them, it's clear that sometimes he's missing the mark. Sometimes Ed isn't even sure of the metaphors himself, but once he has them, he holds onto them - the fish thing has got him especially.
And the thing is that Ed's only just learned to sit with himself in episode 5 and it's overwhelming him. At the beginning of 6, he's the stillest and quietest we've seen him and is gazing out to sea while having flashbacks to things he's done and people he's hurt (hello 1x09 callback).
And the thing is he's okay at the start of 7. He's made a decision about shedding the Blackbeard stuff. He doesn't say anything to anyone and he's ok until Jackie points out Stede is the rising star just when Ed wants out
He doesn't begrudge Stede being excited and happy with his new fame. He is afraid of what his presence has led Stede to: the conversation with Jackie is very much his "you defile beautiful things" moment, especially his presence brought Ned to Stede ("It's me you want").
He also doesn't understand why Stede killed Ned because Stede bottled up his trauma like his love letters. He doesn't even know why Stede a) became a pirate or b) went back to Mary, especially since Stede never actually told him where he'd been directly. He had to hear it from Anne - and Stede is betrayed by that as well ("I told you that in confidence")
Right now, he's feeling unmoored by his own identity and now Stede has taken a step that has fully changed him as a person too and dragged him straight back into the heart of piracy. He tells Jackie he wants out and she asks if Stede knows that and Ed's face just drops and he whispers "shit".
And he spends of the rest of the day thinking and quiet and realises that to process any of this mess, he needs to be away from the pirate world for a bit so he can get his head on straight because now it's roaring back in for him. He sits, he thinks, he realises he needs that space - he should speak to Stede but he tried that the day before and Stede still killed Ned.
Stede also lashes out, which definitely doesn't help. He's right. Ed is panicking, but Stede is also missing so many little clues. Ed never told him about dropping his leathers and Stede just sees him as Ed in other clothes. He doesn't understand the significance, even when everyone around them realises something is off. If even the Swede picks up on it, you know it's an obvious flag.
They both need to use their words and explain wtf is happening with both of them, but they are also both ridiculously traumatised by their past experience. Ed is afraid he's unlovable and now Stede is talking down his coping mechanism, so maybe he's right and Ed-as-Ed is unlovable, while Stede has been told his entire life he isn't enough, so becoming the ultimate pirate should be the win he's been looking for, only Ed isn't happy and Ed is leaving him, so maybe it's him that isn't enough after all.
They are both tangled up so much in their own histories and don't know enough about each others and that's why they keep lashing out and hurting each other so much - they each don't realise what they're saying is a different kind of weapon to the other.
