I would arm yourself today with a tub of epsom salt - it's really cheap and you can get it at the drug store. Then add about a tablespoon to about 500ml of water in a jug, mix it well cos it takes a bit to dissolve then add some food to your fishing net and dunk the food into the salt water a few times then feed the food to the angels. They will might poop like mad afterwards or they might not ... it was hit and miss with mine. Carry this process on for about a week. It won't harm them and it won't harm your tank but it will give you time to look for either an anti-bacterial food or medication.
I'm not saying your definitely dealing with Hexamita but at the same time it could be. In this case I would treat them rather than wait. If you can get an anti-biotic into them and there is something there it'll sort it out. If we're worrying unnecessarily then it won't harm either.
I know how quickly my angels went down with Hex and time is not on their side if it is that. They also infected other fish in my tank