Clown killi male suddenly "shy"

[new_friends]

Hi all, I could use some insight on this one. I have a clown killi tank. At present there are only 2 fully mature adults, one male and one female. There are a number of fry, and I'm working on getting more adults to add - I lost one of the original trio to jumping. So, the male had, from the time we got them about 2.5 months ago, been very visible all the time, out in front of the plants. He'd often chase the female off from the "good" feeding spot (meanwhile I was feeding her in a different spot) and generally pursue her like crazy or chase her much of the time.

About 3 days ago he just sort of stopped being around as much. At first I thought perhaps he'd died but non, he's in there - he just stays inn the back much more of the time. He no longer chases the female every time she's within six inches of him. His tail color doesn't seem as bright. The female has kind of taken over the front-of-tank area and gets first dibs on the food. They both ignore the fry. 

Parameters should be fine; it's actually reading 0 nitrates in spite of the plants so I might need to add some fertilizer. Anyway, 0 ammonia/0 nitrITE/0 nitrATE, pH is 7.1 on my meter, 6.4 on ACO strip, and TDS 323ppm. Temp is room temp, which is currently 72F so on the lower side. None of these parameters are hugely different than they have been with the exception of temperature being about 2F cooler.

Could it be the temperature? The ACO page says they do well at room temp. They had a heater that I gradually lowered to 72F and then removed  (and then some critter pulled it out of my summer tub outside and it melted). I don't see any white patches or other markings. He seems to be eating as much as ever. Ideas/thoughts?

[Kunersbettas]

Perhaps past his breeding prime, or maybe just no reason to display because there are no males present anymore.