Gapeworm infestation can occur either directly by birds eating eggs that have been swallowed or coughed up by infested birds, or indirectly by intermediate hosts such as earthworms or snails. Young birds up to 8 weeks of age are particularly susceptible to tapeworm. Tapeworms normally live in the trachea (windpipe) but are also found in the bronchi and lungs. Typically, eggs are picked up from the ground or from intermediate hosts such as earthworms or snails. The eggs hatch and the larvae penetrate the intestine walls and move to the lungs and bronchi. It is here they go through a larval moult, before travelling up to the trachea. Male and female tapeworms attach to one another once they arrive here. This process takes around 7 days. Fully grown, they are ‘Y’ shaped and vary in size between 1 and 2cm long. They are blood-red in colour (as can be seen in the second photo which shows them in a post-mortem).
And i would worm all of them at the same time just in case any others havent picked it up and just arnt showing any signs