Bettas Fins Turning Red?

I bought a betta back in may for 2016 and he's been in a 3 gallon, and to be fair, he's never been all that colorful. But since I've bought him a new heater he has developed some black and red streaks on his fins, he's still young so maybe he's a koi? Help

This is from when I first got him




Here is a month ago (during a tank cleaning, blue stuff is betta revive)




Here is last week, notice the red streaks in his back fins

 

Is your tank cycled, and have you been keeping up with water changes?

 

Is your tank cycled, and have you been keeping up with water changes?

Yes, and yes, 50% every week. Ph is 7.8

 

Sometimes after proper care for a period of time Bettas start to add color or become more colorful. This may be natural but not for sure.

 

What are your parameters, what do you test with and what is the temperature?