Maybe it’s an accumulation of all of the above, it’s not that hard to work out?
Sounds like the OP tries her best to cater for the household and is on a budget. Comes home from work, cooks a healthy hot meal for the household and probably cleans up afterwards. Settles down for a peaceful evening and then….Just imagining the scene…
DS1 strolls in and starts clattering about making some brownies he saw on tiktok- oven on, flour and cocoa flying about, doesn’t wipe the worktop down. Leaves his empty tins in the sink.
OP is frustrated - the electric bill is as high as she can manage already and she doesn’t understand why he needs to be baking for the third time this week. She tells him so but he ignores her and does it regardless.
Half Hour after that Ds2 gets back and heads to the kitchen - whacks the oven on again as he fancies some sausages for a snack. Clatters about some more, makes more mess. Ignores OP when she mentions that the oven’s already been on twice that day, and she’s already cleaned the kitchen three times.
Once he’s gone DS3 is down, decided he’s starving despite being 10pm and fancies some chicken nuggets even though there’s fruit or a bowl of cereal he could have. OP suggests these and is told “no, I’m doing chicken nuggets in the oven and that’s that”.
As a parent of young adults I can totally understand why she gets pissed off - it’s the lack of respect, ignoring her, making a mess, doing hot snacks to make that mess when a quick sandwich would do. It probably feels like they’re running a short order cafe in her kitchen that she has to pick up the bill for and clean up after.