I think they're in two gallon containers. I'm pretty sure it's a nitrogen deficiency; my last watering was the first time since they were 12 days old that I didn't use any nutes because though I saw no negative effects I haven't heard of anybody feeding with every watering. So the last watering five days ago, I gave just water.Then the bottom leaves started yellowing. I haven't checked the pH in a while, though, I'll do that tonight. Maybe I just diluted the nutes too much or something. Anyways I'm just gonna keep feeding the way I was before from now on until flowering.
On a side note, the only time the cat can get in the grow room is when I'm in there.
And I'm VERY relieved that they're likely gonna be fine, I'll stick to the more gentle suggestions from now on. Thanks a lot for the replies, people. Most of my (albeit inexperienced) knowledge about growing I learned from lurking on these forums.
Edit: spelling errors bother me.
and eat the weed
I just looked at that picture. Looks like my cat. 
