So I beat skeletron prime, The Twins, The Destroyer, and The Wall of Flesh (in that order) but in chat it doesn't say: The jungle grows restless... what do I do? Do I have to fight all the mechanical bosses again?
Killing the Wall of Flesh for the first time in any given world triggers hardmode, which is when the Corruption/Crimson and Hallow 'V' is generated. It is also the first step to the path to the Moon Lord boss. Though you can summon the mechanical bosses on any world (even pre-hardmode), the "jungle grows restless" message will not trigger unless you beat the mechanical bosses after the world is already in hardmode.
So in summary, you beat the bosses in reverse order - you should have killed the Wall of Flesh first, then the mechanical bosses. Now that you've got WoF beaten, you can beat the mechanical bosses again and the message will appear this time.
First of all, check if your world is in Hardmode. Easiest way to do so is to see if you have a natural Hallow biome in your world as the Hallow only exists in Hardmode. If it doesn't, kill the WoF. That should make the Hallow generate and in turn initiate Hardmode. After that, defeat all the Mech Bosses(they do not have to be killed in any order, however I suggest killing Destroyer first). A message should appear saying: "The jungle grows restless..." During this, Plantera's Bulbs will start to spawn. For more information, check the wiki.
It is impossible to kill all the mechanical bosses before the WoF. But, you may have killed the Eye of Cthulu, Eater of Worlds, and Skeletron instead of the mechanical bosses. But, if you did defeat the WoF before you defeated the mechanical bosses and then defeated the WoF again, then I do not know what is going on. It may be a glitch or you just have to defeat the bosses again.