How to improve my ECs?

Hello! I'm aiming for T20 admissions and I'm worried my ECs are a bit below the level of a usual admit. I was interested in getting advice about what to do next with my time to improve my chances. For context I'm a rising junior and I plan to major in bio or env sci. Here are my current ECs for further context

Academic decathlon (Won several golds at the state level and a bronze in science at nationals)

Writing a book on environmental issues of lake Erie (On track to finish by end of junior year)

TikTok account explaining science topics by connecting them to media (spawned out of boredom, not too many followers)

Marching band (Band got best possible rating at states twice, quit after sophomore year)

DND (Not my top EC but I have to organize a group of people and write a lot so I figured it was worth including)

I have the time to do things I just don't know where to go next. Any advice is greatly appreciated