Tips of my air plant are starting to turn brown. Any suggestions?

Question

The plant sits in a shell on the window sill and is watered by soaking for a minute with filtered water (no chorline)other than the tips,it looks healthy

Answer 1

Does any water remain in the shell after you soak it? If so, that needs to be removed.
Here's a good article on how to deal with problems with your air plant:

https://www.gardeningknowhow.com/houseplants/bromeliad/reviving-tillandsia-air-plant.htm