Sunken Belly Peppermint

Got 2 females that I bought with sunken bellies, my mistake didn't inspect properly before purchase from private seller for 1 and the other got given to me with the purchase of some healthy ones. Been trying to get them back into condition but don't seem to be having any luck. Would really like to get them back into survival contention the picture is of the worst one the other being about 50% of the sunken belly. If you guys have a process or any tips I should try that would be great hate losing a fry here and there let alone big girls like these. Had these fish for 4 & 6 weeks now.

Tank size and setup: 12 tanks - 1600 litres All share same water Temp 24 degrees
Substrate: Gravel/Slate/Driftwood
Filtration: Large Sump/65 litre bioball drip filter,
Airstone/sponge filter etc: No airstones / Poret sheets in sump
Inhabitance: Tank with sick fish 5 peppermint females 12-7 cm / Total system 900 odd bristlenose and a few crs
Fish affected by issue: 2 Fish/Sick when purchased due to me not looking over them properly.
Feeding system (what, how much, how often): Algea tabs and zucchini/cucumber at all times.
Water changes made since illness appeared: 40% every week.
(pH 6.5-6.9, Ammonia Low range, nitrate low range, nitirite low range
any chemicals used (including carbon/chemical fitration inside the filter: none
water source and treatment: tap water no treatment
Symptoms (gasping, not moving, bloated, spots, wounds, stressed colours etc): Not eating, zucchini should be eaten but doesn't appear to have much eaten in the morning compared to other tanks with just two pepps inhabiting.

Just a update I found a post by kfenk http://www.bristlenoseworld.com/t3514-heat-treatment-for-internal-parasites and decided it was worth a go, moved female to isolated tank and raise the temp to 33 degrees and low and behold next day when I dropped in zucchini she went to town on it so hopefully Ive found a solution in time.
Will leave her at the high temp for another three days then lower it back to 25 degrees and see how we go but fingers crossed.
Think I should give her some protein blood worms or something to help build up fat stores?

Anthony

It's nice to hear you might of found a cure and I hope it works for you & the peps but remember that if you give protein give little at a time and build up slowly. Please let us know how she goes.

Bns are herbivores. Sure, she'll eat worms and meaty food, but it might be hard on her stomach.

3Rd day doesn't seem to have eaten anything substantial over night. Another two days and I'll drop three temp back down.

after 4th night doesn't seem to have eaten again with the zucchini going untouched
maybe when I return to normal temp shell get back on the chomp