This actually happened to me as well when I was in the over world. A few times. But has happened to me as well. (happened let's say about hour 20 minutes ago)
I dunno what the /gamerule randomTickSpeed is set to. It is/was on a public server. But on a singleplayer world (1.2.5 updated to 1.15 then moved through the snapshots to the recent one) which a farm was growing alright, but slowly.
Sorry for the late response, was gonna get back sooner, but yes. Seems like the same/very similar issue I am having on my world.