Hey, Chicka is correct on the dose. Remember, Wazine will only paralyze any worms (round) in the chicks/hen's body. This prevents a toxic protein reaction if the worms were to die all at once inside your bird, could kill it. Once it is expelled to air, it dies. Any eggs shed in the soil, will be consumed and restart that cycle.
Once you have treated with Wazine, you will come back with, a wormer that will address the eggs and future outbreaks. I like Valbazen. You will no longer use the Wazine from that point on for routine worming.
This is just a brief overview, if you would like, PM me and I'll send you my research/recommendations and protocol. Your 14 week old chicks are fine. Are they presenting with droppings/worms? (looks like spaghetti) If you like, go ahead and wait a few more weeks on the younger ones, unless theyt are showing signs of worms, etc.
My thoughts, if their feet have been on the ground at 8 or 9 weeks, they need to be wormed. Especially in the south's humid/hot/wet climate.
Thanks and hope this helps.