Hi and welcome to the forum
As Aiken said, if it's been like that for 3 weeks and hasn't changed, then it isn't white spot. It could be excess mucous caused by something in the water irritating the fish. Or it could be an external protozoan infection. However, ich-x treats external protozoan infections so unless you used an expired bottle of medication, or you seriously underdosed, it is unlikely to be an external protozoan infection. Epistylis can be treated with ich-x so that can be ruled out too.
If you have to treat white spot, use heat (30C/ 86F) for 2 weeks or use a chemical based medication (ich-x). Don't use both together and don't add salt as well because all chemicals, and salt, reduce the oxygen level in the water. Warm water also holds less oxygen than cooler water. Having a combination of salt, chemicals and heat can deplete most of the oxygen from the water and cause severe stress to the inhabitants.
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Did you add anything to the tank in the 2 weeks before this started?
Did you remove carbon (black granules) from the filter before treating, assuming there is carbon in the filter to begin with?
What is the ammonia, nitrite, nitrate and pH of the aquarium water?
What sort of filter is on the tank?
How often and how do you clean the filter?
How long has tank been set up for?
How often do you do water changes and how much do you change?
o you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?
Did you use a full dose of medication?
What are the tank dimensions (length x width x height)?
What other fishes are in the tank?
Do you use hand sanitiser, moisturising cream, or have grease, soap or anything that leaves a residue on your skin?
Do you have buckets and hoses specifically for the fish tank?