All of the S. haddonis that I have ever kept (( been keeping them for 15+ years )) now, are super sensitive to flow -- the slightest change will cause them to move.
Have kept them in a 75, 65 and 58, and couldn't go higher than 60% on my MP10's (( 2 of them )). In addition, they were always be right at the rock/sand interface, with the foot buried under the rocks --- attached to the bottom glass.
Have you done any water changes since you removed the E. quadricolor? Have never been able to mix the 2 species.