I have contacted my local authorities they said its mosaic virus and cannot be treated. Should we use 1kg of naoh for making 500liters of pesticides?  

It seems excessive to use sea salt every week. Once every 3-4 weeks would be good.
Judging from the shape of the leaves, it seems that the problem is not caused by a disease.
The occurrence of certain pests frequently causes the leaves to curl.
If pests are a problem, try adding 1 kg of NaOH.