My hotspot for my balls are around 88-89. I've found that mine prefer the bit cooler temps as when I an issue with the thermostat probe coming partially untaped they hot spots were 91-92 and they didn't really like it.

Again this is purely what I've noticed from keeping balls the years that I have. Most people that I know keep their temps around 88ish as well. Maybe try lowering the temps down slightly and see if you notice any difference.