Swordtail too old?

#14
When I fed the fish this morning Trinity swam up to the surface like she always does. She didn't eat the food but rather floated back half way down. Then she swam back up and did the same several times.

Now she is lying in the corner, sometimes sideways, and is breathing really hard. She doesn't move around anymore.

Luckily, Neo is leaving her alone, taking interest in Starlet.

She's not eating, not moving, and breathing hard. What should I do?