Heritage Audio OST-4 , 500 Series rack - properly turning it on and off?

Quick questions, I have an OST-4 here with 4 different series 500 modulers in there, for context a neve 1073lb, a neve 535 compressor, an empiricabl labs derresser and a maag EQ4.
Before, i had an OST-8 which had an on/off button, but i downsized a bit cause i was only using these 4, but this new OST-4 unit doesnt have a power switch. Whenever turn off my powerstrip where the OST-4 rack is connected to, the unit makes a pretty loud popping sound (not even through the speakers, i tried this without it being connected). It sounds pretty unhealthy to me, but since the OST doesnt have a power button, i dont know if its alright to do it like that. Or should I just keep them running? they get a bit warm, so it doesnt seem super amazing to me to have them on all the time. anyone got experience or advice?