Possible overdose due to my stupidity

[epitidios]

I have my flock into tiamulin, due to respiratory problems. This morning, i had the really bright idea to use half of the medicine in the water, and the other half with the bran they eat. Now one of the chicken has problems with walking. Is it possible that she ate to much bran and got an overdose? Any ideas on what to do?

Thanx in advance