Loaches are sensitive to meds. Tetras are sensitive to water conditions, so they may/may not survive the treatment. Try to avoid the meds, increase the temp slowly over time to about 82°F (28°C), and perform allot of water changes. If your fish indeed have ich, the increased temp would speed up their lifecycle.
Could you post some info about your tank?
What's the size of your tank?
What are it's tank mates?
What are the ammonia, nitrites, & nitrates levels?
How often do you do gravel cleanings?
How often do you perform WC (water changes)? What percentage of water is removed?
How often do you clean your filter? Is it the same time when you do gravel cleanings?
Sorry for the lots of questions, but it would help narrow down what could have caused the illness in the fish.
Also, if only 1 fish have it, chances it could survive without the other fish getting it. Just do not stress out the fish and keep the tank clean and well maintained.