Lot's of data being written on SD card

So, i set up an OrangePi PC with armbian just to run pihole+unbound about 4 or 5 months ago. Out of curiosity i ran

cat /sys/fs/ext4/mmcblk0p1/lifetime_write_kbytes
31366225

That's 31GB written on the 8GB sd card which is almost empty

df -h
Filesystem      Size  Used Avail Use% Mounted on
udev            430M     0  430M   0% /dev
tmpfs           100M   11M   90M  11% /run
/dev/mmcblk0p1  7,2G  1,7G  5,4G  24% /
tmpfs           500M  3,5M  497M   1% /dev/shm
tmpfs           5,0M  4,0K  5,0M   1% /run/lock
tmpfs           500M     0  500M   0% /sys/fs/cgroup
tmpfs           500M  8,0K  500M   1% /tmp
/dev/zram1       59M  8,4M   46M  16% /var/log
tmpfs           100M     0  100M   0% /run/user/999
tmpfs           100M     0  100M   0% /run/user/0

Checking the data written since the last reboot 91 days ago

awk '/mmc/ {print $3"\t"$10 / 2 / 1024}' /proc/diskstats
mmcblk0 11032.2
mmcblk0p1       11032.2

11GB in 91 days.

I checked the logs. Nothing out of the ordinary. The biggest files are the pihole logs (around 5MB per log which rotates daily)

iotop -a shows that journaling writes about 1MB of data per hour to the disk.. that's still only 2GB per 91 days

Is there a good way to see what exactly is writing so much to the SD card? Thanks in advance.