Khuli Loaches Inactive?

So I have 3 striped khulies that have been in my tank for about 6 months. When I got them, they were extremely active, and were very fun to watch. But recently, they haven't been coming out very often, only for food. Another thing though, is that I was gone for about a month, and a relative of mine took care of the tank, and he only cleaned it out once.
I clean out the tank every week, about a 30% water change.
So, now that I'm back (and have been back for about a month) my kuhlis aren't very active like they used to! I checked the water, did plenty of water changes, and have been feeding them their favorite foods (peas and bloodworms). I don't know what is wrong with them, all of my other fish seem fine, and there are no physical signs of them being sick.
I don't know what to do, I miss my fun little eels!
Any advice appreciated!

 

Any ideas?

 

Well, what are your water parameters right now?

 

Nitrite 0
Nitrate 5
Hard water (150)
Chlorine 0
Alkalinity 130
Ph 7.8

 

Oops, I was wrong. I'm used to my kuhlis doing the "happy dance", but they don't do it anymore, even when my water is ideal. Maybe they are used to having clean water and are lazy?
Is that even possible?

 

Kuhlis are more active in the evenings & at night as that's when they're out looking for food, also the more you have the happier they are & more likely to be out & about more

 

Yeah, they aren't as active at night anymore.They used to swim all over the tank at night. But now they just sit around and only move really when its feeding time.