Bettas From Walmart

Hi, i just got two betta fish from walmart and one looks like it has little pieces of it's fin missing, possibly finrot?
And the other is wierd. It is swimming around just fine, but on the edge of it's back fin, like a border, is fringed with black. And one strand of its fin is pure white. This is why it's wierd for me as it is not clearly an infection or fungus because i cant distinguish spots anywhere else. Both fish are swimming fine.

What is this? I would post pictures but it says they are too big, sorry.

He's kinda darker tinted on the end of his body, and yeah. Thanks

You can resize picture through something like photoshop if you have it or photobucket (its free)
 
Difficult to diagnose anything without pictures and need a bit more details of any symptoms.
 
But does sounds like stress to me but thats just being generalised. 

We gotta see pics to tell you what it is.

The fish with black fringing the end of its tail


Nw the other possibly fin rot

yea that most likley is fin rot, by the looks of it.

How would i treat either of these?
On both fish? Or just one? And how do i treat it? The betta in the first pic is in with other fish, so i dont wanna upset them.

im no expert on finrot by all means check out this link http/bettasplendid.weebly.com/fin-rot-101.html
Could you QT the fish that doesnt have it?

The second one that you think has fin rot is too hard to really see the edges of the fins to be sure.  The fact that they came from Walmart or any other big box store that keeps them in the tiny cups makes it highly likely that it does have fin rot.  The way to treat fin rot is very clean warm water and high protein foods.  What size tank is the second one in and what temp do you have the tank?  
 
The first one looks pretty good. The black edging looks to be coloring and not something to worry about.  He really looks like he is regrowing his tail which seems normal with the clear part of the tail.  What size is his tank and what other fish are in the tank with him?  

im thirteen and i dont have any more money or another tank. i have another mason jar but i know they shouldnt be kept in those unless they are big. the other jar i have is only 1.5 gallon, too.

So do you have a heater in either of the tanks?

the other fish is in a ten gallon tank with four "assorted platys" they said at walmart it would live nice with them. its cute they chase each other around but dont nip, i watched for aggresion, dont worry. they are all buds. both the fish are swimming around nicely and look happy, they all ate this morning. they both were definetly happy to get out of the little cup the only thing they did for a long time was swim around the entire tank, like so happy to have space.
what would be considered high protein food?
 
i want to get both of them as best as they can be. i noticed on the one with black on it's tail it has a little circle of darker tail twords the end of its middle tail. the first thing i thought of was external parasite??? but then i looked closer and it looks like maybe the gender? i dont know, i will try to get a pic but they move so darn fast!
 
the temp for both the tanks is 80-82 right now.
i have a fully submersile heater in both

Be aware that platies can be nippy and betta fins are perfect for them to nip.  Watch the 1.5 gallon jar as it could easily get too hot.  It is hard to heat a container that small reliably.  It is also very important to keep that jar very clean or there is no difference in the tiny cup he was in and the jar you have him in now.  He needs 100% water changes with water that is as close to the same temp as possible every day.  High protein food is frozen brine shrimp, bloodworms, or a good high quality pellet food like New Life Spectrum betta formula.  

Now i see a darker spot on the top of his head right where his gills end.
And his scales are outlined in brown. Coloring?

That looks to be coloring.  Did you take the time to cycle your 10 gallon?  If not, then you need to be doing 50% water changes every day to keep the ammonia down to safe levels for the fish.

i suppose its not the time to say that platies are unsuitable for the 10 gallon tank.