Putting live plants in aquarium all fish staying in the bottom of the tank?

I have a 40 gallon fish tank, full of goldfish. And my prize fish..an 11 year old comet that I got at a carnival in the 6th grade haha. I work at a pet store..and recently brought home a few live plants to add a bit more oxygen to the tank [i have an air wall covering part of the back wall for oxygen]. I added two mondo-gr, and a java fern. Lately, all of the fish are staying in the bottom of the tank. Their tank is heated, for the plants and the pleco, so i know it's not too cold for them..and hibernation isn't for a couple more months correct? Why would they be doing this? Normally they are insane..practically jumping out of the tank when it's time for food..now we have to tap the gl to get them to come up. I'm concerned, they are my babies :[ All were feeders that i saved from getting eaten..