Unfortunately I lost all four of my clown Loach not long ago, two of them were over seven inches. I never really had a problem with my Loach's fighting, occasionally they would have a go at each other , I remember one occasion the fighting lasted several hours and then abated and they went back to being friends again.
I suppose we would give you the same advice as we would with Oscars, see how things go and if it is quite obvious that one Loach is taking a bashing and injuries are being caused, you may have to take it back to the shop. Just make sure you give them plenty of hiding places, mine used to have a great big plant pot that they would enjoy huddling up inside.
Apart from that, I haven't really got anything else to offer