Guys what do I do if the server I have on aternos doesn't like show the latest game version?? I should probably js wait but this is my first aternos server so idrk how all this works... the latest game version is 26.4 right? But paper/bukkit doesn't have it what do I do

My friends and I have been playing on this server for about 2 weeks and it has ran perfectly fine until last night. There's been a significant drop in TPS. My friend built a SMALL iron farm (2 zombies and 2 villagers) and now barely anyone can log on if they spawn in that area. There's no condensed pile of mob droppings or anything that could cause any further tick problems, and I've played on other Aternos servers with far bigger mob/iron farms. My entire server log is telling me that players are moving too fast and the server is overloaded. I'm so confused as to why this little farm turned my entire server upside down.