There is often construction debris in the water lines. In many cases the strainers get clogged up and reduce the flow. It would be worth removing the strainers off every fixture and flushing the lines to remove the debris.
It could also be a kinked line in some cases.
I would disconnect the water line from the toilet and flush and check the flow without going into the toilet. If the flow is good, then you may want to see if the toilet has a strainer that may be plugged.
Did you try and remove the little diffuse device at the top rear of the bowl...3 little holes that shoot the water around the top of the bowl? That could be clogged also. I'm not sure how to remove it.
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Traded Thor for Melbourne Prestige 24NP
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie
Blondie passed in 2020 at 5 to Leukemia