Shiro also the same situation as Kuro as the amount of chakra between him is dwindling down and it was already in miniscule amount but at least the invasive water chakra is now doing harm towards the knight rider and it's stead.
The two flame power have decrease in power significantly and the water chakra is still continuing to ravage throughout their bodies.
The two were breathing in a much more heavy manner than before their fire energy is clearly running out and because of their attribute the water chakra deals more pain than usual.
Not only that water chakra deals pain it also makes them extremely uncomfortable so the knight rider sword play became awkward as if he did put force in his attack.