Sunflower deformed leaves

Hi. I have grown some giant sunflowers and red sun sunflowers this year from seed. I planted them out into the garden a couple of weeks ago and just last week I noted that four of five plants planted in the same border were displaying deformed curled leaves. After doing some research I believe this to be a result of aphids, which I could see in clusters on nearby cosmos. I have applied an insecticide but would like to know whether I should cut back the deformed growth or just leave the plant be? Photo attached.