Slow Blinkers need help!

If the change in flasher rate came with the alternator / battery issue that is likely still the problem. If amp gauge twitches with the flasher operation the entire charging system has a problem. If the charging system is proper a couple of flashing bulbs or even hazard flasher operating all 4 wouldn't effect it.
Owners of these older cars seem to believe that a weak charging system and headlights that dim and brighten with engine rpm is normal. Not true. When the car was new its charging system was adiquate.
Replace the flasher ( located on right side of ashtray hanger ) if you like. Good luck with it.