i also have the same problem with my sand star my blue legged hermit eats it and i have enough food and my tank is 75 gallon and only 1, 4 inch hermit is present what else is causing these problems ?
is the 1st pic a juvenile purple tang juvenile tends to have there body coloration more bright i also have a purple tang but mine sometimes bright and some times pale it changes color or your is always drab in coloration and also check your water parameter maybe its stress
reef safe medication is very ineffective in my experince because they say that it wont harm your inverts but what is ich its an invert so it means it wont kill the ich it will just make your fish skin more resistant to the parasite but when you stop putting the medicine it will come back again qt tank is still the best and proper nutrition and diet that is the only way to prevent them try aquamedic exodin that is the most effective medicine i tried so far that is reef safe the other one i have is very very effective but not reef safe its home brew from the philippines ther is only one shop there making and selling it
put a skimmer you cannot have a marine aquarium without skimmer specially you are just starting then cycle your tank properly about 1 to 1.5 months put bacteria to seed your bio filter and use sump as filtration it is the best overhead sucks canister is ok if you know how to properly use it and get a denitrator to reduce your nitrate its sounds complicated at first but as you go along you will understand how to keep marine fish happy fish keeping
i have an ich infection my desjardini purple majestic and red wrasse are all affected but today at last after 2 weeks they are now getting better i use aqua medic for the medicine and put jbl vitol into there food and also put garlic and also vitol into the frozen food and finally clip ah red algae for them to boost there immunity it helps for me proper nutrition and less stress for the fish is an effective method of preventing ich