Ah, I see now they are the fish sold as red honeys not natural coloured honey gouramis. Sorry about that mis-identification
These are not actually honey gouramis. They are either red thick lipped gouramis or some say that are honey-thick lipped hybrids. I have never been good at distinguishing the sexes of this fish
Having said that, I suspect the fish on the right in the first two photos is female due to the shorter rounded fins. The single fish in the last photo is possibly male as its fins are longer and not quite as rounded. Of course I could be completely wrong
With true honeys, I could usually tell the difference in the shop tank by behaviour. Males would be the ones with an up front attitude while the females tended to be minding their own business and searching the bottom of the tank for bits of food.
So hopefully you do have a male and female.
It's possibly the one you got a week ago is slow at settling in. The brown poop is a good sign; it's white stringy poop that often means internal infections, anything from bacteria to worms.
You haven't mentioned nitrite, hopefully that too is zero.
Nitrate is a bit high at 40 ppm, it is now realised that levels above 20 ppm are not good for fish long term. What is the nitrate level in your tap water? UK legislation allows up to 50 ppm in drinking water. If your tap water is also high in nitrate, there are things you can do to lower it in the tank such as using nitrate removing media. But if tap nitrate is low, your tank nitrate should be at just about the same level as tap level. If it's higher, the usual causes are not enough water changes allowing it to build up, and/or feeding too much fish food as that decomposes to make ammonia which is turned into nitrate.