I need some help with my Oscars' health please.

[Piicklez]

I've got two Oscars' and there are a few things potentially wrong...

Firstly One of my Oscar's has what appears to be HITH, this started as one little hole and now there is quite a few over his head and on his gills, they also seem to be getting bigger. I have left this until now because I did a little research and came to the conclusion that it wasn't HITH, but I'm not sure now. Another thing is that the same Oscar always wants food, any time I walk in to the room it swims to the glass, and it never used to be like this, is it sick?

Also, I have another Oscar which has gaps in it's fins, it started out as a hole but grew to about the size of a pea and then broke the edge of the fin, and this has happened twice now on the top fin.

I'm sorry for not having any pictures or anything, I know how its hard to say anything without pictures but I was wondering if anything that I have described may be common illnesses with these fish?

If anyone has any questions about specific details I can explain further, and maybe someone could give me some advice on what to do?

 

[Redbellypiranha]

its a vitamin c deficiency and poor water quality

 

[Piicklez]

Oh, really? How do I add vitamin C? Also, I have been slacking with water changes, I used to change 25% every week, now its more like 20% every 1-2 weeks.