Brief Answer:
Pitting type nail

Detailed Answer:
Hi,

Thanks for question and photographs.

I saw that only few nails have some pits on the nail plate and other are normal in the pictures. So this is a local cause as against any serious disease. Besides I do not see any discolouration of the nails. If the pittings are more uniform on each nail plate and on all the nails then we should start investigating other causes.
Generally pitting nail plates are seen in Psoriasis, Eczema (long term skin infection) Alopeicia (hair fall) Reiter’s syndrome (arthritis).
Since you do not complain about joint pains, scaling on skin or scalp, itching anywhere else I do not be worried about it.
I know this is cosmetically bothering you this because of superficial plate growing and water washes that away leaving the pit there. You can apply vinegar / tea tree oil on the nails. You can try this once a day for a month.

You can see a beautician as well for better results.

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Brief Answer:
Psoriasis and eczemA

Detailed Answer:
Hi

I really understand what is going on your mind. I know you want to rule out serious things.
Psoriatic arthritis and other infectious arthritis was in my mind. Fungus was also a reason.
To know the exact cause, it needs an examination and if required biopsy of the nail bed. By careful examination under magnifying glass we can be 95% sure.
Please see a local dermatologist for the same. they can see under magnifying glass under well lit conditions. They scrap and send for biopsy as well.

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