Insufficient data provided. You need to size the common vent separately from the vent connectors. Here, I see a large B-vent all taped up with what appears to be a B-vent tee snout connector that then transitions to single walled vent connector. You use separate tables for the sizing of the connector and vent.

There is insufficient support of the connectors.
There appear to be 4" connectors on 3" draft hoods.
You can manifold multiple appliances but it must meet the code sizing and bottom line, it must work . Has anybody tested this installation? Do you have other issues such as makeup air? Any signs of spillage or condensation?

Sediment traps are ALWAYS required by code whether enforced or not.

Bob

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