Need help with common vent

Two vents entering in a common vent, the smaller vents are below the bigger vent but they enter in the common vent past the bigger vent in the horizontal plane. Is this acceptable?

No backdrafts observed
The small vents are same btu ( 2 water tanks)
Bigger vent is furnace
Thanks for your input.

My opinion…The rear gas fired water heater flue is connect to the front gas fired water heater flue, which may cause combusted fumes back to the front water heater and back drafting.