[toolate_frozen]

Personally I have never seen velvet on an african cichlid. You should be able to see it if they have it, try using a torch or catching the affected fish and viewing up close in good light. How long ago did you administer these treatments? Also, what are your water parameters and setup?
Ammonia/nitrite:
Nitrate:
Temp:
pH:
Tank size:
Fish in tank:
Filtration:
How long has tank been operational: