Help! Random branches dying!

So over the past three days i've had two random branches on the bottom of my plant die. There was no yellowing in the leaves or signs of a problem. I just checked on the greenhouse and the branch was wilted and dead. No signs of bugs from what I could see but the branch was separated from the stalk quite a bit. I know it was broken from me or my buddy so not sure what could have caused this?

Also, the plants around it are starting to yellow pretty bad in the bottom. I just switched to flower so want to get this figured out asap. Thinking its just a nitrogen deficiency because its only effecting one strain, but anyone else's opinions would be appreciated.

I've had rodents take off low branches. If no teeth marks it might be caused by a rodent jumping onto the branch. Bait some traps and see if you get anything.

N cal mag. They are like a domino effect when you have one or the other deficiency. Feed it that, pull off the yellow leaves so you can see if it fixes it after feeding it N cal mag. Its a typical deficiency. And once you start feeding her flowering nutes she'll really start to come back

Could be lack of light to lower branches.