Sulfur conundrum

Every June, my well water (normally perfect) goes a bit foul till around September. I’ve had a few tests done, and usually they come back with no issues. I’m leaning towards it being hydrogen sulfide gas as I can leave water out in a glass and it’s fine the next day. A carbon filter (like a bretta) works well, but I’d like to do the whole house so my showers don’t stink.

I’ve added in a carbon canister filter, which is also removing the smell/taste, but it’s absolutely killing my flow rate (can’t flush a toilet and run a tap at all, about .8 gpm with filter on)

The neighbor mentioned that he had some sort of nozzle outlet on his well that feeds his holding tank (we are all on tricky systems with 5000l holding tanks in the ground) but I’m not finding much info online about such a thing. Either a whole home high flow carbon filter or whatever witchcraft the neighbor has would be great, if anyone has any suggestions!