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If you're really sure the symptom appeared right after the static discharge, then something in the front end of the amplifier may have gotten damaged.  However, that sounds rather far fetched.  Scopes should have protection against these kind of events.  Were all the effected channels connected to some equipment at the time?  Is is possible that the mechanical jolt of you bumping the table  caused the equipment to short the scope inputs to a high voltage?

How are you deciding there is an offset?  I'm not familiar with your particular model, but there must be vertical position settings for each channel that make any offset somewhat arbitrary.

I would look in the service manual of the scope and see if there is a zero offset adjustment.  You probably have to open the box to get at such adjustments.  I have seen scopes with zero offset trimming capability per channel.

If the offset is too large to be able to be trimmed away, then something really did break.  In that case, unless the service manual gives you a lot of detail, you need to send the scope out for repair.  Nowadays, manufacturers don't supply the kind of information required for you to do your own repairs.  It used to be equipment like this came with schematics, but that's not been the norm now for decades.  Without a schematic, you have no hope of being able to diagnose this yourself.  Even with a schematic, lots of stuff now happens inside proprietary chips that are only shown as black boxes on the schematic.