A 5-1 loss to Stuttgart on Saturday followed a 4-0 defeat to fierce rivals Borussia Dortmund on February 20.
Schalke have won just two games in all competitions since November, lost seven of their past nine matches and only scored two goals since January 24.
Their alarming form has left them bottom of the Bundesliga with just nine points from 23 matches during a chaotic season in which they have had already had four different head coaches.
Gross took over from Manuel Baum at the end of December, with David Wagner and Huub Stevens having previously been in charge.
After picking up just five points in 2021 and having been knocked out of the DFB-Pokal by Wolfsburg, Schalke have taken drastic action in a bid to arrest their decline while planning for life in the second tier in 2021-22.