Only the water evaporates. The salt is left behind, so just add more bottled water to the tank.
You're only supposed to feed about once a week, so they probably had enough food.
I aerate my tank once a day when I'm at work. I don't aerate on the weekends. If there is algae, you don't need to aerate as much.
My friend's relatives have tanks that they have totally neglected, and the Sea Monkey's are thriving. I feed and aerate like clockwork, and mine are good too. Some people claim that less is more. Others say that aeration is very important.
So... keep doing what you're doing. I would give them something to eat if it has been a week and the water is clear. If you can't see their digestive tracts (a dark line in the Sea Monkeys), then you definately should feed them.
I hope this helps!
LisaH