guppy tail

Hi, I have a 15-gallon tank and 30 guppies in it. Their water ph and ammonia in a moderate level, I also have a sponge filter running 24/7, But recently 1 female guppy who is not spreading its tail, and 2-3 males are also starting not to spread their tail. I am guessing they are doing this for...

So I have has what I believe to be a lyretail guppy for about 5 months now, and I've always noticed something wrong with his tail. His actual tail fin is perfectly fine, but his longer pieces have always looks like they have been cut. I though it was my other guppies in the tank, so I watched...