Yes, saying that "All fish have and carry ich" is up for much debate. However, this only holds true for hobbyists. There is no controversy among the scientific community. The evidence all refutes the idea that "All fish have and carry ich."
Are your clownfish wild caught? Clownfish are very suceptible to brooklynella, otherwise known as clown fish
disease, although it can infect other species of fish. The best treatment is a series of three formalin dips at 1cc, 1ml or 20 drops/gal of 37% formaldheyde. That does NOT mean 37% formalin and 63% water!One treatment every third day. Use only in AERATED dip for 45 minutes. Be careful not to injure the fish with the net (I don't use nets if I can help it.