that sounds normal behaviour though. Clever fry stay under cover and just dart out for food before darting back. Just keep doing as you are and if you think you are over feeding cut it back a bit
I just found it weird because my other two batches of swordtail fry I've had never hid behind anything, they'd gather in on the food. They would also swim around a lot. I didn't have plants but some rocky decorations back then.
I will reduce the flake size and feed twice a day.
I just hope I won't find the other calico dead too. I looked over the internet, and it seems like swordtails with black pigments are the most sensitive. -.-