Tps lag despite server not utilizing all resources

So me and my friend created a modded mc server. It's in forge 1.20.1, has around 100 mods, and uses godlike.host. We have 8gb/1000% CPU plan. At a time we usually have 4 people online, hut it peaks at 7. But here's the issue: We have really bad tps lag. If it's 2/3 ppl, it's usually okay. Tps stays at 17-20. But if any more get on, it drops really badly. With 7 players it usually sits around 10-13. And despite all of this, on godlike it says that our server is only using between 5 and 7 out of the 8 ram, and only 150-350% of the 1000% CPU. Is there anything we could do about this? Can we just like force the server to utilize more resources? Thanks In Advance