Whats your tank temp at? I noticed my Africans breathing heavy before when I had a temperature spike to over 85! Do you have powerheads or air stones running for water circulation? It's good that they aren't sitting on the bottom, that would be bad. Also, make sure you soak your pellets in a cup of tank water before feeding to avoid bloat, when your Africans eat pellets that you dump into your tank the pellets will expand in their stomach and make it difficult for them to digest, which can lead to bloat.