I am seeing this trend that chandrabindu is being replaced simply by the anuswar in some words, especially in plural words such as ‘bhavnayein’, ‘patrikayein’, etc. and also from some verb forms such as ‘dhundhna’, ‘pahuchna’, etc.

What is the correct spelling for these words and are both spellings (with chandrabindu and with anuswar) allowed and considered correct?