Musty insert smell

My FB inserts are faintly musty-smelling and I'm not sure what to do. It's usually not a problem but when they are damp (not quite dry on the line) or in the dryer (propelled air) the musty "left-over" smell is definitely there. Is this what tea tree oil is good for, or is that just for in the bucket? BTW I wash in Persil, I tried a couple of eco samples (bounty pack) but found it worse than Persil.

I never remember to strip the nappies/inserts but always add a couple of drops of tea tree oil to the wash and we don't have smelly inserts/nappies

Maya wrote: My inserts used to be really stinky but I started adding a capful of Dettol Fresh to the rinse cycle and now they're much better

Same here except I use Canesten, as well as treating the smell we use it mainly to make sure our nappies are not harbouring any extra bugs that might aggravate Erin's rash.

I haven't had a problem with the Canesten so far, and have been using it for nearly five months. Anything in too great a quantity would have the potential to cause build up I would think?