PLEASE HELP! male guppies is ill

I’m new to having an aquarium...I had my tank set up for about 2 weeks before I went and bought any fish, I have a 54l tank and bought 3 corydoras, 3 guppies 1 male 2 female, 2 gourami and 1 pleco. The first day they were absolutely Fine but i noticed my male guppy had a clamped right fin but he seemed happy enough following the girls around fine eating fine. The next day I went to feed them and I noticed a pale white patch on him but it looked like a blister and he was flashing on plants a little I thought maybe he had been bit cause he has still swimming fine and eating fine but today I woke up and went to feed them like usual and he was at the top of the tank away from the females and he had another spot forming on the other side of his body he isn’t going down to the bottom of the tank and he isn’t interested in food or the girls anymore. I’ve checked the water and everything is fine, tonight I’ve noticed that my pleco and one of my corydoras are flashing on the gravel now. Should I go and get a treatments for him or just tank him back to pets at home. I have no idea what it could be or what it’s from. 

i don’t want him suffering but I don’t want all my other fish to go the same way. Please give me any info you have...many thanks Ok hand tone2Ok hand tone2Ok hand tone2 I managed to get a few pics.