I think again about Seunghyub's letter it's like he confides to us. I feel something like a depressed tone in his word but he tried to look cheerful.
He wants to show that he is still working hard even we can't see that. He really wants to show us the song that he makes, but +

+ but he is not sure too when they can be released a new song.
He must be sad GMF canceled but thinks N.Fias are sadder so he said sorry. He said spending the same days, it must be not much that he can do and he doesn't really like it. But he wants us to not worry about that +

+ so he said he do his daily life by following the rules.
About the fishing, I think he just wants to tell he still has a good time with the members.
And to make us less worried he put that fish picture to make us busy instead, searching the name of fish type