You can use that if you wish. Do keep in mind that Enrotex is Enrofloxacin (Baytril) which is banned for use in poultry. It is a very good antibiotic and sometimes a vet will prescribe it off label. Do some research on whether it's suitable for your use or not.
She has just come out of molt?
If so, then she may be having a little difficulty coming back into lay.
Does she have anything leaking from her vent? You mention yolk and a soft shelled egg - there's what looks like a soft shelled egg and a membrane in the photo. IF the contents of the...