Minecraft 1.13 Mob spawn rate

After about 4-5 hours of gameplay on a server with multiple people in varying locations mobs have stopped spawning in regular numbers and spawn at a rate of 3-5 an hour. all settings to fix this have been tried peacefull to hard and restarting, spawn distance for mobs is corrected to 20 blocks via commands slime chunks offer no slimes and loaded and unloaded chunks have been tried. No torches are around for theses tests and all caves are empty in the area i stand.