The more I think about this the more I feel your fish has bacterial fin rot. Here's a few medications you can try......
https://aqualabaquaria.com/products/acriflavine-ms-velvet-medication-fish-vet
https://www.chewy.com/api-furan-2-f...3yJJI5mpVbqpApq7zet36buRR7lJLUawaAjdtEALw_wcB
https://aquariumplants.com/products...Jvbvd5rs7qyCUnxnvcc8nNvzP9AgfSAIaArLuEALw_wcB
https://www.chewy.com/api-triple-su...sB1Rp_n-taa9r4p7ZSZwwRYjA_BfF3qkaAm_OEALw_wcB
?? I'm confused. Why would her sub, effect how she treats her fish?With that type of substrate you will be battling water quality uphill, in the snow, on a slip and slide, getting sprayed with a fire hose and getting chased by a doberman that shoots bees from its mouth.
Because it's going to present an ongoing issue with water quality that will most likely only get worse with time. Extremely messy fish should be kept in easy to clean tanks. 4" of large river rock is going to let poo fall to very bottom of the tank where it will remain.?? I'm confused. Why would her sub, effect how she treats her fish?