I kept aficans and clown loaches together and they did well
They do get white spot if stressed and I would say yours have definitely been stressed, I used to treat mine with a very mild addition of salt when they got it but have to be very careful with loaches and salt as they have no scales and it can kill them, some seem to have success with the high temps and aeration so guess that cant hurt just watch them.
Regarding food mine just cleaned up what if any scraps there were after the africans ate, I used to chuck in crushed up shrimp pellets and I guess they got some of them and whatever else hit the ground..