How Ice formation works:

According to Minecraft.gamepedia.com in the section talking about "ice" (and in my experience with the formation of ice in minecraft), water source blocks are only supposed to turn to ice when it is exposed to the sky, the light level next to it is below 13, And there has to be at least one block next to it that isnt a water source block (though gamepedia just says water). Due to this, water is supposed to freeze from outter area of a pool of water in a cold biome, to the inner area

Do note: Both the "Ice" section and "Water" section of the Minecraft Wiki both talk about ice. The difference is that the water section just doesnt go into depth about ice.

Problem: 

Water seems to completely ignore the "no horizontal water source block" rule (One block that is horizontally next to a water source block, must not be a water source block in order to naturally freeze a water source block), and now just freezes anywhere. I was standing at the edge of a 50 x 50 pool, and noticed that the first water source block to freeze was directly in the CENTER of my pool! Followed by a bunch of random water sorce blocks freezing just everywhere in my pool.

How I figured it was a bug**:

The pool that i was just talking about, is in my minecraft world and is exposed to sky light. It has remaimed in the form of water over the past year because i put a solid block over the outter most water source blocks of the pool so that they wouldnt freeze because of the lowered light level. Without those blocks freezing, the rest of the water sorce blocks couldnt freeze because every water source block would have nothing but water surrounding it.

All of my farms have been destroyed due to this issue