I have dates in column D in Google Sheets.  I want the cells to highlight red if 30 days have passed and there is not a comment date in column F.

*Example:* 

Column D:  Submittal Date  6/29/2019<br>
Column F:  Comments Received (date) 

If I don't receive comments within 30 days of submittal date the cell should turn red to alert me to follow up.