So I got 5 green chromis on Sunday. They were all happy and good as far as I could tell. I came home from work today and the tank lights were off, so they were all chillin on the floor behind the big rocks, sleeping I assume (9pm). I turn the light on for a quick feed before bed and I can only find 4 little guys. One is laying on his side behind a rock. UH OH! So I get my net and try to push him around a bit. He flips out, swims a little, then back down on his side. After that it was over.

The other 4 are fine, swimming around eating, no problems.
Double checked my salinity and temp, 78F and 1.024 salinity!
What I'm not sure of is how much to feed right now. I have a frozen food peice, which my LFS told me to break off a peice about the size of my finger nail (pinky), soften it up in RO or tank water then dump it in. I'm also adding pod food, about 1/2 a tsp a day, just to try to keep the other stuff alive as well.
Am I feeding enough? The LFS said to feed once a day, that fingernail sized peice of food. Again, this is for 5 green chromis. I guess I'm curious as to what you all do for feeding or what you would suggest for me?
72 gallon tank, 75 lbs of live rock, 40 lbs of live sand, sump setup, 1 power head and return.
Thanks for any help!