Yes, I stand by my statement that if your fry are at the top, you should be worried and do a water change immediately. After today's 20% water change with OceanFree Super External Bacteria & Fungus Away, the fry are now idling at the bottom searching for food.
On a side note, baby brine shrimps do not survive as well in fresh water as compared to microworm. Although microworm are easier to harvest and culture, the yeast that goes together with them fouls the water pretty fast. But they can survive up to 2 days in the tank.
Baby brine shrimps are much harder to culture, but since they're salt water creatures, they are virtually parasite free. Baby brine shrimps carries their yolk sag which is packed with nutrients. But because they die off within 3-5 hours in the tank, those uneaten (fry seemed to ignore those lying dead) will rot and produce ammonia (remember the nutrient packed egg sags? Bacteria loves nutrients!).
Both brine shrimps and microworm will foul the water. As long as you do not overfeed and do regular water changes, all will be well.