Fungus?

[BettaPony]

One of my platties has a weird muddy brown side(normally orange), all the other platties are fine but betta is laying at the bottom and not moving, is not separated neither is betta because my quartine tank is ick infested and i will remove my betta tonight and put in a canning jar(can't do much better), I would like to avoid quarantine if at all posible, the best i can do for quarantine is 2.5 gallon filtered and unheated, because of high nitrate i will being doing a water change tonight, I hope this just high nitrate and a water change fixes it please help
Tank size: 20 gal high
pH: 6.5
nitrite:0
nitrate: 60
alklinity:40
hardness: 50
tank temp:78 degrees Fahrenheit

Fish Symptoms (include full description including lesion, color, location, fish behavior): betta- laying at bottom, not eating whatsoever platy- muddy brown on one side, weird dark red on head, snails are trying to climb out

Volume and Frequency of water changes: weekly 10%

Tank inhabitants: 6 platy, platy fry, dwarf gourami, betta, 3 snails

Recent additions to your tank (living or decoration): none

Digital photo (include if possible):

 

[BettaPony]

https://www.pinterest.com/pin/255297872610576639/

 

[FroFro]

One of my platties has a weird muddy brown side(normally orange), all the other platties are fine but betta is laying at the bottom and not moving, is not separated neither is betta because my quartine tank is ick infested and i will remove my betta tonight and put in a canning jar(can't do much better), I would like to avoid quarantine if at all posible, the best i can do for quarantine is 2.5 gallon filtered and unheated, because of high nitrate i will being doing a water change tonight, I hope this just high nitrate and a water change fixes it please help
Tank size: 20 gal high
pH: 6.5
nitrite:0
nitrate: 60
alklinity:40
hardness: 50
tank temp:78 degrees Fahrenheit

Fish Symptoms (include full description including lesion, color, location, fish behavior): betta- laying at bottom, not eating whatsoever platy- muddy brown on one side, weird dark red on head, snails are trying to climb out

Volume and Frequency of water changes: weekly 10%

Tank inhabitants: 6 platy, platy fry, dwarf gourami, betta, 3 snails

Recent additions to your tank (living or decoration): none

Digital photo (include if possible):

Is your tank properly cycled? Are you treating with any medications? How much food do you feed your fish and how often? Are you using water conditioner when you do water changes?

You also need to be performing water changes of either 50% once a week or 30% to 40% twice a week. When you do water changes do you also remember to siphon the gravel to remove poo and uneaten food? Excess decomposing organics in the water will only increase water parameter spikes in an uncycled tank and cause further stress. Do an immediate water change, wait, test your water, and change again until your readings are in safe ranges.