Change styling on main block only (of a linked block group)

So let’s say I have a certain amount of blocks from the same type, for instance a Div.
They are all linked, so when applying a change to the 1st block, all the other blocks will pick up the new styles.

What is the best or most elegant/efficient solution to make a specific change to the 1st block only without affecting all the other ones?

Resetting all the other blocks one by one is a possibility, but can’t be the solution.
Setting up a Relative Styling class combinator with a first-of-type pseudo class could be a possible approach.

What is recommended?