I just checked my load data versus your after reading SAHUNT's post
where he mentions "I like my bullets not to fast. I believe you get
better terninal balistics at a lower speed." which I totally agree with.
Velocity doens't kill game.

Back off your loads a fair bit and work up as SA HUNT says.

I think you are going WAY too fast for some of those bullets and
this is proably affecting accuracy.

Try 75 - 76 grains of ADI 2209 with 300gn bullet and work up
Try 68 grains of ADI 2209 with 350gn bullet. I have loaded up to
74gns of 2209 for mv of 2375. You can probably go higher but why ?
Long, Heavy for calibre bullet that kills well at 2375.

Max OAL is 3.6 on a 375H&H - stick just below that and don't change too many
things at once when reloading and testing otherwise you wo't know what is causing
the change.