As long as your surge supressor is rated above the combined amps of your ballast you should be fine. I could be wrong, but I think the only real improvement would be to have 2 seperate surge supressors. Not that you have to. But, that would isolate them from each other some more. If I remember right the outlets are not, on most, isolated from each other.
They should have no problem at all on one thou, just typing outloud.