Easiest thing to try is to swap the EF86 tubes and see if the hum stays in the same channel. If it does not, then you have a tube that either needs replacing or its pins cleaned.
If the hum stays in the same channel despite swapping the EF86s, you can experiment with the 6922 tube.
If you have a spare 6922 tube, try it instead of the one installed now.
Other obvious things to consider: have you moved the Eros recently? Or moved something else closer to it? The hum could be coming from a nearby source.