Thanks Vishfood and everyone else.
I was frustrated by the lag I've been experiencing since yesterday afternoon until I found this thread!
1 - I had to figure out how to turn my developer options on since it's not just automatically there like it used to be, but I didn't see the option I was looking for (select runtime). So I'm assuming it automatically changed to ART and I can't change it back and forth? If that's not the case, can someone possibly tell me where that option is? Just for future reference.
2- Tried the power off, wait 10 seconds, power on. No change.
3 - I tried just turning off the in-app sounds for Facebook a bit ago, before getting to page 3, and that helped a little but not enough.
4 - I entered Recovery mode after my phone was off for like a minute to clear the cache partition.
THIS worked. I'm not sure I would have ever thought to do this without this thread. lol. <3
5 - Even though I mostly fixed the issue, I was still lagging with messenger then I saw Vishfood's suggestion to turn off Use NuPlayer. This greatly helped as well as clearing the cache partition. I'm not sure I understand his comment about what it's for, but it's making my messengers work properly again...so thanks.
I'm also not sure how my battery is doing yet since it was fairly low when I started fiddling with it to figure out why it was laggy. Hopefully improved, like you all have mentioned! I did note that it now feels almost as fast, if not faster, than when I got the phone and first used it. I should point out that my phone was so laggy last night that I accidentally sent my friend 10 of the same hug smiley on messenger. XD
Oh, one more thing: So Fast Boot is not longer available? I mean, it doesn't seem to need it now, but just curious if it's completely gone or just moved? I think that's everything I wanted to say...Maybe.
Thanks again everyone.