Multiple discolorations in newly poured concrete slab

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We undertook one of our first home improvement projects this past weekend and had our small, builder placed back patio slabs demo'ed and had 2 new, larger concrete slabs poured this past Saturday. It's now Wednesday and one of the slabs (the larger one) looks fine while the other, smaller slab (pictured) is showing various discolorations and surface differences.

The other slab and area outside of the box all look uniform; grey with white speckles (which we understand will fade and even over time).

The area of concern is in the boxed area, where there's areas of black discoloration in some parts, while another piece of this slab looks bleached white compared to all the rest of the concrete work. It also seems to have a different surface consistency than the rest of the concrete.

I've read about treatments that can help with discoloration, but since there seems to be various discolorations going on, not sure the right approach.

Given we're newies at concrete work and the contractor has been of little help, we're reading all sorts of information online. Did a search but didn't see anything that speaks to treating one area with multiple discolorations/surface variations going on.

Should this be treated or will it even out over time? If treated, what would be recommended; vinegar, muratic acid or a commercial treatment of some kind? Would it work for both the black spots and bleached looking area?

Many thanks to anyone that has advice or expertise they could share.

q multiple discolorations in newly poured concrete slab
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