Collections missing from Google Index - Sudden Drop in Indexation

[seanysean]

Hi

We run an online Opticians store and retail more than 100 brands.

Virtually all of the 'collection' pages eg ray ban sunglasses, oakley glasses are no longer in the index.

Also other collections such as kylie jenner sunglasses have dropped, in this case from position 1.

The issue is not affecting 'pages'

I would appreciate any help / suggestions?

Sean