It takes months for corals to recover when they are pale........not weeks.
Get more snails if you are concerned about some film/hair algae.
A lot of people lose their way because they get so obsessed with a little algae.......... they put all their efforts into eliminating that and lose focus on what's important...........the corals.
Some algae growth is good............it's natural to have a spike in algae growth after removing your GFO. It will take time for the system to start a new balance........again think in months not weeks.
Once your coralline algae starts to thrive it will choke out a lot of the film algaes.
Put your Hanna away for a month or so and just let the tank adjust.............watch the system and be patient.