my smallest plant is now dying!

So this started about 2 days ago. I havn't been able to figure is out. My other plants have light mg def. that i'm treating today.
I thought it might be that or that fact that i was going to transplant last thursday but i'm waitng for my pots. Let me know, I don't want an epidemic in my grow!

wdf transplant that shit.

Yes transplant, and it does have Mg def.