My question is if we worm the peas 2x's a year with Ivermectin and Safegaurd, are they safe from blackhead or is this something that just comes along from a bad worm they get and is not preventable??? Then can't we worm pea chicks under a year old or do we have to wait till they are how many months? The 2 babies are only 3 weeks old is there a dosage for them?