What happened to make them stop being energetic?

With my cherries, if i notice them being slow, its because my nitrates are over 5 or something else is going on in the tank.

Do they perk up after a water change? And you say the water is normal cause you had it tested. Was it with one of inaccurate testing strips?

Water conditon's defined as normal,fine,good, don't mean much.
Number's for ammonia,nitrites,nitrates offer a more comprehensive view of aquarium condition's.
Would NOT rely on other's determination of what water in my tank's was like but would purchase a test kit such as API Freshwater master kit and perform my own test's.
I got ton's of shrimp and they crawl about fairly slowly over the substrate ,plant's and only time they are super active are when male's are out looking for females to breed with.
Cooler temp's can also reduce activity level's while warmer water increases metabolisim's and activity level's.
Critter's/fish don't appreciate sudden changes in either.

I had this when my ph dipped really low, all the shrimps clustered togther in a corner.. Removed all the driftwood and they resumed back to normal. With abnormal behavior, it is usually a change in parameters that they are not comfortable with.

Right after I feed mine they are less energetic,... it's almost like they are less determined to move around now that they are full and don't have to hunt for food.

The next day (I feed every other day) they are back to flying around the tank, playing and foraging vigerasly.

Whiskey

Was the food fed a high protein base food? I read a post on shrimpnow discussing potential downside of feeding a high protein base food causing lethargic behavior in shrimps. Kinda like you after eating that turkey on Thanksgiving. Can't find the source ATM because I'm at work, but it was an interesting read.

if they were zipping all over the tank and then just stopped and kinda mosey along grazing now it would have been mating. when females molt they release hormones to signal to the males. males will go nuts and fly all over the tank in the water column. with that said it could be a change in parameters as well.