Why is my goldfish missing scales?

I have two fantail goldfish, both maybe ... six or seven months old at the very oldest. Their names are Mac and Tosh . This is Mac; http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs323.ash1/28326_122557011107203_100000587149589_201321_5647078_n.jpg And the orange-striped one is... show more I have two fantail goldfish, both maybe ... six or seven months old at the very oldest. Their names are Mac and Tosh .

This is Mac;
http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs323.ash1/28326_122557011107203_100000587149589_201321_5647078_n.jpg

And the orange-striped one is Tosh.
http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs323.ash1/28326_122557034440534_100000587149589_201322_7984629_n.jpg

I am not sure at all of their genders, though I have been calling Mac a female and Tosh a male.

Last weekend, on Saturday, we moved them to a new tank, a 10 gallon. They have a Marineland power filter, a Penguin 350 for up to a 70 gallon tank. We were finding it impossible to keep their water clean for more than two days. Now, we can already tell that the tank is much cleaner, and everything is looking to be a lot better. We added brand new rocks to the bottom of the tank along with a fake tree branch/plant ornament in one corner. Both of my goldfish have been hiding behind it, over in the far corner of the tank, and I'm not really sure why. My assumption was that maybe they had laid eggs, but I don't see any.

Then, yesterday, I noticed that Tosh had a large section of scales removed from one side, a patch of maybe ten or more scales just gone from his body. A few bits of his lateral line are missing, as that is around where the scales were removed. Tosh has always had a fixed bend in his left lower caudal fin, so he swims with a little extra effort normally, but now I have noticed that it is even harder for him to swim in the direction he wants to go.

So I was wondering, why are his scales removed ? Could Mac have possibly bitten them off him, or could they have fallen off ?
(I would get a photo of his missing scales, but he moves too quickly for me to get an accurate image)

Also, is this something I should be worried about ? Will his scales grow back eventually ? Is this something that needs immediate attention ?

Thankyou for your time and comments, I really appreciate anything you might have to say to help my little fish !

3 answers 3