It definitely looks like a deficiency. How was your CO2 doing when you left?
Truth is, you weren't around so you can't be sure what happened. If your tank was doing well before you left, keep doing what you were doing then.
I'd suggest removing any unhealthy or dead plants, salvage everything that's still healthy, and replant. Whatever those new pests are they're going to have a field day on any decaying leaves. If you want to avoid their population exploding you need to remove anything they could use as a source of food.