Yes. the silver will tarnish, but the rate of tarnish will be greatly affected by the temperature and relative humidity of the environment of storage. At higher temperatures and higher humidity, the rate of tarnish will increase.

Perhaps a change in the color of silver (loss of gloss) is related not to oxidation but to the formation of a thin layer of silver sulphide on the surface. The more sulfur compounds (hydrogen sulfide) in the air, the faster the silver surface will cover with a dark coating.

maybe

Mystery solved (back in April)! The new batch was kept in a vacuum chamber. Four months later they exibited a blackish colour. I later found out that another item in the chamber had a sticker on it. Glue is often rich in sulphur. The silver acted as an absorber and developed a silver sulphide later (as suggested in other answers). The first batch I produced in June 2018 was kept in a drawer and remained shiny. That is why I believe that the tarnish is due to silver sulphide (and not silver oxide), which develops in sulphur rich enviroments (e.g. humid air).

Silver oxide is really unlikely to form (unless you have a significant presence of ozone or other strongly oxidizing agents), while even traces of sulphur-containing compounds easily tarnish silver, even in absence of humidity. See the article linked below and the references therein:

Article Silver Tarnishing Mechanism Revealed by Molecular Dynamics Simulations