Low mob spawn rates

[NEKOMENACE2 Guide 12]

I have noticed a severe drop in spawn rates for hostile and non hostile mobs and was just wondering if anyone knows why this is.

[_Casanova Admin 36]

Has it been when a bunch of other people have been online?

[ZTolerance Admin 86]

Yesterday I had to same, I think I saw one Zombie all day (and it killed me!) I even unlit a whole area to see if any spawned but nothing. I was alone on the server most the day. Just logged in and the dark area was swarming with mobs so seems it may have corrected itself. 

[HOOOSK Owner 608]

This isn't due to something that we've changed.  It has to be something within Minecraft itself.  We'll do some investigating.

[ZTolerance Admin 86]

perhaps an april fools?

[Miku Forum Mod 132]

The drops are low on survival, yes.