Q.Foxtail fern
My potted foxtail has started turning brown in the center. The outer / older fronds are fine, but the inner ones are turning brown in less than a week after I trim the already dead ones.

This is a common symptom of root rot. Make sure the soil is well draining. Allow the soil to dry out a bit before watering again.
Cut back any stalks that look dead.
https://www.gardeningknowhow.com/ornamental/foliage/asparagus-fern/foxtail-asparagus-ferns.htm