Feeling super discouraged with the white paint on my Tau

I finished painting some Space marines and felt ready to take on my army of Tau. I used thin coats of white but for some reason it looks chalky and clumpy. idk if its just because of the white or what I'm doing wrong here. Im using a Rustoleum flat white primer that leaves the models smooth and clean, a Vallego Dead White 50/50 mix with water, sometimes more water. Then a Nuln oil wash, i like the dinginess to it but it might be too much in some places. Any advice before i continue to butcher 30 more tau troops would be greatly appreciate thank you.

EDIT: pics

https://preview.redd.it/1w36if3phbyd1.jpg?width=1283&format=pjpg&auto=webp&s=7c4628716c1702725e86d35b7c92f4d3079a84f1

https://preview.redd.it/a2nwzw2phbyd1.jpg?width=1013&format=pjpg&auto=webp&s=603e726796888102c9ed09fc87840b9ae6ad7c5d

https://preview.redd.it/nsragt2phbyd1.jpg?width=1178&format=pjpg&auto=webp&s=99b20d7b36f9e84e057b2fba8569b5ee6825ce12

https://preview.redd.it/q7e90t2phbyd1.jpg?width=942&format=pjpg&auto=webp&s=ee48f1c355f8d500be403802fd80ffe19a843987