RDS postgres slow read IO

We are running postgres 14.12 in rds and expirence very slow IO reads.. around 30MB/s on index scans. we can't figure out what might be the cause of it. any ideas to what we should / could check? **configuration** instance class: db.m6idn.8xlarge (which should support 3125MB/s throughput) RAM: 128GB vCPU: 32 storage type: gp3 with 25000 IOPS (we only reach 18K) and 4000MiB/s throughput. most of our slow queries are due to slow IO read..