the pigeon has what is a respiratory infection of the upper nasal tract, teas will do the job for a while but it will return, you did the wrong thing medicating for canker , worms etc ... do not treat pigeons blindly , you do more harm than good, by treating blindly you damage the immune system and hence the reason the infection returns, why people treat blindly i never know, panic maybe.
Follow the following instruction, leave the pigeon well alone for 2 weeks to rebuild its immune system, then treat with TYLAN ( antibiotic) for 5 days 2.5 ml to 5 pints of water, then electrolites for 3 days in the water as per instruction on the box. Then follow proceedure again , this ailment should then be cured and well gone, other than that the cheaper option is 1 drop of neat TCP down both nostrils other day for 4 days. ( do not exceed this)
Just remember when buying in new birds, that the equilibrium in your loft is different to their old loft, they need to adjust to things, they are animals not just a bird !!!
call me if you need help 07989 746150 spencer