i havent done some horse stuff in a while so. lets go
 
1.) When Birdie was born, Twilight and Dash had an agreement - if it was a unicorn, Twi could name her, if it was a pegasus, it’d go to Dash, and if it was an alicorn, they’d have to come up with a name together. and well, second foal comes around, and Dash most certainly isnt going to forget this deal - and stops Twilight right in her tracks before she can even think of a name.
 
He was born on a scorcher of a day in the height of summer. So, obviously, Rainbow named him heat striker to reflect that (and also it was p wonderbolt-ish, and cool and epic. this tiny snotty foal will be a great flier one day, trust Rainbow she can tell).
 
 
2.) Of course, once Summer got his cutie mark, the name was changed to Summer Ballad (still keeping with the theme of heat/warmth from his birth, but more in line with his talents) - but following these (https://www.deviantart.com/uunicornicc/art/Raise-Your-Glass-843165039/https://www.deviantart.com/uunicornicc/art/Summertime-858753144) - Summer took a very big shift in attitude. Wanting to distance himself from anything feminine, he starts using his old name, and agrees to take up more serious/intense flying sessions with Dash.  
Rainbow loves this, and is blindsighted by the excitement of one of her kids finally taking an interest in her special interest - that she completely overlooks how uncharacteristic this is of Summer, and that something is clearly wrong.
 
3.) Twilight notices, though. he grows distant from her especially, and she notices him drifting from all the things that make him happy. she tries to pull him back, or to at least give him some support during this time - but he pushes her away.
 
She’s being a mum here and trying to get him to take a scarf flying, at the very least. you can be a top flying wonderbolt but youre not immune to frostbite.
 
4.) His realisation that oh yea wait he hates intense flying, why did he sign up for this.
 
5.) Like I said, his whole demeanour changes - and it’s not just Twilight who notices, either. Iris is his best friend, and they frequently hang out together - but he stops doing that as often as he used to, and when they do spend time together, something is clearly wrong. she’s usually a care free airhead, but seeing her best friend like this… just doesn’t sit right with her… and she’s determined to do something.
 
 
pony content is taking more effort from me recently. these are collections of stuff ive done spread out over the past month rlly, bc idk im just not motivated for it rn. it comes and goes in waves, ive just got to ride things out