It is ideal if both the SmartThings and Phillips Hue hubs are operating on different channels than the Hubitat Hub.
I don't know of any way to turn off the SmartThings hub's ZigBee radio, but you can check its chosen ZigBee channel by logging into the SmartThings Groovy IDE, going to the My Hubs tab and then scroll down to the ZigBee section to see the channel.
If by some chance, the SmartThings hub ZigBee channel is also 13, you could try shutting it down, removing the batteries for a minute, and then starting it up again, which may force it to choose a different ZigBee channel when it sees another hub is using that channel. Otherwise, it may be necessary to do a hard reset (one user mentioned it quite a while ago here, but I don't know how much that messes up user settings. I would search the ST forums to be sure.
I don't use a Hue Hub, but I remember reading the channel can be changed via the Hue App.