is this fin rot

[dnelli]

I thought my baby beta was ripping his fins on plants so when I got his new 2.5 gallon tank I got the silk plants and his fins grew back and have been normal for almost a month but all of a sudden the fins were getting smaller and looked ripped and today I noticed they look a little black.Is this fin rot? Also can anyone tell me what kind of beta he is and how long does it take for them to become full grown?

[Hannam135]

I think so.