Rapid algae growth and algae on catfish?

[Whiteboi_J]

HELP! got a 55g cichlid tank with 6 medium sized cichlids and a big hifin catfish that has been up and running for 2 weeks now. did a 15g wc yesterday, and now today most of THR has major algae growth when there wasn't any like this yesterday, and the hifin has same looking slime all over him as does the THR. NONE of the other fish look like this. See water quality and pics below

PH - 8.0
AM - .25
NI - 0
NA - 10-20

 

[Lupin]

Does the slime coating look yellow/golden from your personal view? Even with flashlight pointed on it? I'd separate the fish immediately. This may be velvet. The only treatment useful against it would be Mardel's Coppersafe.