Am I Deficient? Need help ID'ing deficiency

Hello,
I've noticed my plants have some yellow discoloration along the edges near the veins. I'm not completely sure what's going on. Could it be a cal/mag deficiency? Here are some photos of young and mature leaves that show signs.

What do you feed it/how much per feed? Frequency?
What's the medium?
What kind of lighting do you have them under?
Temp? Humidity?