Guppy & balloon molly doing this
So my ongoing guppy saga, sadly, continues. My cobra guppy now seems to have somewhat of a 'bald spot' on top of its head and is zooming. This was just noticeable today. I got him 22 days ago. He seems to be swimming normally and eating. I have one female guppy left, and this male guppy that pretty much killed all my female guppies due to overstressing with mating, does not even touch the female. There are two cobra guppies and one female.
I also have balloon mollies and notice them rubbing on gravel and decor a few times. Water cycle was done yesterday - 20 gallon tank - and I tend to do it once a week on Saturday, due to the excessive waste of the mollies and 3 platys.
Nitrites and Nitrates are zero, so is ammonia (yellow.) The ph I check with drops and is blue not dark blue or light. I check it with strips too and the color, to my eye, hovers around the 7.5 mark.
What could be the problem? I just added API stress coat two hours ago. It's roughly bedtime now, so should I add more stress coat in the AM too?