Sulfa for 30 days and no improvement - I'm sure it's not cocci unless you're seriously misdosing her. IN which case, you probably just made sure the coccidia you left behind are resistant to sulfa drugs.
You have a couple options. First, take her temp and evaluate her overall health. She should be a good weight, growthy (birth weight plus 10lbs per month of age for a dairy kid - so a 3 month old born at 8 lbs should be around 38lbs or more)
At this point, you can try mechanical control for her gut, in hopes that it is not bacterial infection and is just upset from being on antibiotics/antiprotozoal drugs for 30 days. Kaolin pectin, and lots of probiotics. Lower grain intake and increase hay/alfalfa pellet intake. If she's not used to alfalfa pellets, don't introduce them. Evaluate the diet and management to see if it could be feed or sanitation related.
You could take her poo and any others with clumpy/runny poo and do a fecal parasitology exam and if that's clean, send the poo to a lab to do a bacteria culture.
You could continue to guess and deworm them with a QUALITY dewormer and start them on an oral antibiotic to clear up a contagious organism such as E. coli and Salmonella, which are fairly common. (If you do this, I STRONGLY suggest putting them in a fresh pen so they don't just pick it back up again from the environment).