Hi, i have a 55g tank set up for 4 years. It currently has 3 1.5yo angel fish and 1 4yo gold fish with 1 4yo pleco. My youngest & smallest angel fish is white with black stripes. I noticed 2 days sgo it wasnt wanting to come up and eat. The top of its head has turned a orangish color. I just did a 50% water change yesterday and noticed its staying at the top of the tank and taking frequent sips of air. Still no interest in food this morning. All other fish are normal. The 24g of water i added to the tank was distilled bottled water since we are on a well and the last time i changed 50% with it it killed my 3yo b/w striped angel. Its head turned the same color but i don't remember it keeping to the top of the tank. I have a video but looks like i can only upload a picture to this site. What do i do?