What are the symptoms of a weak alternator?

I'm experiencing some problems like
1 - blinking dashboard
2 - When I try to start the engine, it does so slowly as if the battery is weak though I tested it and it was fine, with the car on and off. (Voltage)
3 - Sometimes lack of response when it's idle, as if the engine is about to turn then when I push the throttle much more the problem go away.

Are these all alternator problem?

A guy mentioned that he changed the alternator to solve the dash board blinking issue.