Ok long question for those with patience:

1950's halcraft house, 4 ton AC unit 1500 sq foot house, my two eastern bedrooms which get a lot of sun are temp measured 5-10 degrees hotter than the rest of the house, that is a lot worse than it sounds when you try to sleep in 80s.

I've put some baby shade trees on the east wall and a trellis, both rooms have blackout curtains and fans, I also literally have rerouted the master bathroom duct with temporary duct work into the master bedroom, so I can't close my master bath door, but honestly it's helping... a little, and noticeably blows better than the registers from the two rooms that heat up.

So today after 3 years of misery I decided to go up in the attic myself, an AC guy had been up there and told me everything was "normal", after going up I suspect he didnt go all the way back. Here's what I noticed:

The very cool rooms in the house, including the master bathroom all have flexible duct work coming off the AC. The bedrooms in question though seem to have solid metal ducting that I suspect has been there since the house was built. I say suspect because that's all I can find, the flex duct clearly doesn't go to the rooms, it seems like solid metal ducting is buried under insulation, I also couldn't say for sure, but some of the insulation felt really cold which made me suspect a leak in the ducts but I couldnt find anything, it's blown insulation which is a pain in the neck when you gotta work in your attic.

What are my cheapest options to fix up my two rooms? Or ughhh.. the best and or most expensive options?

Does this sound like a duct issue or something else?