Guppy with clamped fins

I woke up this morning and noticed one of the male guppies had clamped fins and would not eat. He is hanging around the top of the tank and all the other guppies look fine. I just did a PWCyesterday and all the params today are normal, I am going to do a PWCtoday again. I was wondering if I should add some aquarium salt or quick fix? I did also have a nitrite spike the other week.

My params are 0/0/10. I did a regular PWC yesterday and another today, roughly 5 gallons. It is a 15g with a Tetra whisper ex20. I have 6 total guppies and 4 ramshorn snails. The tank has been running for 5 weeks, only 2 weeks with fish. Guppies will be 2 weeks tomorrow and the snails 1. They have 12/12 lighting. I feed 2x a day with NLS pellets and the occisonal algae waffer for the snails. Water temp is 80*.
I went to my trusted LFS today and he gave me Maracyn Two, which I dosed. I think this might be a bad lot of males that I got. I picked up 45 females from one shop and they are all doing great. I bought 2 males from another and 1 died within a few days.

He is losing color, it looks faded. He is still not eating, I just tried again. He is hanging in the front left of the tank just left of the filter discharge. He looks small maybe an inch, maybe an internal parasite?? He hasnt been pooping so I really cant tell. He doesnt seem to be gasping or bloated.

His caudal fin looks shriveled now. Almost like Gyrodactylus? He looks so sad, I hope he makes it...

woke up this morning and he has died. Thank you for your help.