Sick chicken

[kay-chckn]

I posted a little while ago about my hen, I ended up consulting a vet because she didn’t seem any better, the vet told me to change the wormer I used to kilverm, I used it and my chicken seemed fine for a day but then went back to runny poos and seeming lethargic, I’m having to wash her bum again as it’s getting hotter here and I don’t want her to get fly strike or anything like that. I had also trimmed her bum feathers to try avoid more poopy accidents. I really don’t understand because she’s feeling lighter but still eating and drinking and rummaging around the garden, she is the only one out of my 6 brown shavers to be acting this way and I don’t know what to do