i've had my small RBTA for about three months. i feed a small piece of shrimp weekly. it stays in the center of the tank and never has moved, so i think it's pretty happy. but it's pink, instead of dark red. and it's tentatcles are looking skinny, and not bubble tipped. It's under LED lighting. I don't know all the parameters of my tank, but I do a weekly water change. Any ideas on why it's not dark and bubbly?