My evergreens in the front of the house have done fantastic since I've planted them a few years ago. But all 4 of them have started to grow what looks like deformed leaves. Does anyone know what causes this or what I can do to fix it?

Not really much you can do now bar prune those plants: this is damage caused by aphids on new growth, most likely shortly after you pruned the plants. The leaves will just continue growing deformed due to that damage.

In the future just keep new growth in check for any signs of aphids and eliminate the buggers promptly when you see them.

You are saying the plant will grow deformed for the rest of its life? And there is no use trying to treat against aphids now ?

No, THOSE leaves won't change but new ones will be normal unless aphids get to them too. Use just about any insecticide as the new growth starts and you should be able to prevent similar damage in the future.

varchar8 said:You are saying the plant will grow deformed for the rest of its life? And there is no use trying to treat against aphids now ?

Aphids are gone now, and won't be back for a long while. It's useless to treat against them now and usually no prevention is done since they have no easily predictable behavior: one year you may get nothing and the next be swamped by them. The only solution is vigilance during the warm season and quick treatment.

When aphids feed they may cause damage to new growth that will cause that growth to become deformed and or discolored, just like you are seeing. This specific growth won't heal, so you may want to prune it to allow the plant to develop new healthy growth to replace it. The plant as a whole is not affected: it's a highly localized mutation.