The brown part looks normal. The urate is quite yellow and if I am not wrong also quite brownish. Ideally it is white to light yellow.
From what I know, this could mean two things: Either he has retained poop for a longer time in which case it can occur that urate is more on the yellow side. Or - and most likely - you will have to increase misting and monitor that he drinks properly. I would try to increase the length of the misting sessions first.