As shown in my signature, I'm still on KitKat, so I was just curious about what you were seeing. These phones are not known for low light... they basically suck! To suck in LP even more than KK, is really bad!
When you say the "resolution" is better in KK, do you mean the photos in LP seem more "grainy" or "noisy"? Do you remember if the LP photos were a little "brighter" than in KK?
If they increased the max ISO setting in LP, (which is what they would do if they did anything to the camera) then the photos would be brighter, but they would also look more grainy. Higher ISO = more noise = makes the photos look like a lower resolution.
I'm guessing here as I really don't know if the LP update even touched the camera firmware. But, I would suspect that if they did do something, it would be with the ISO settings to help low light situations... with the sacrifice of more noise.
EDIT: Well after posting, I quickly went out to do some research and found that LP did in fact upgrade some camera functions. Supposedly, they are improvements so they're supposed to help.
HERE'S an article I just found.
No consolation if you're not pleased with the changes to your camera, but you weren't imagining that the camera changed going from KK to LP.