Flower question with pics

Hello ,
I have 1 Auto Assassin , and 3 Auto Berry Ryders.
They are at day 55 with 600wHPS.

The auto assassin looks almost done already , it is only 10" in height and is covered in trichromes that are still clear.
The 3 berry ryders also are at day 55 and are about 18" in height and is covered in trichromes that are still clear.

The berry ryder Kolas have gaps where there seem to be pre-buds that have not "popped" yet , should I let them go another week or two.
I also think they are root bound. most of the big fan leafs have turned yellow and fell off.

Here are some pics.
1st 2 are Auto Assassin



2nd 2 are Berry Ryders. Circled in red is what I think is a pre bud , that has not popped , correct me if im wrong please:

It's natural for the leaves to turn yellow and fall off at the end of the flowering cycle. Some people use grow nutrients during flowering to keep them green, but they should naturally change. Let the trichomes tell you when they're done. What size pots are you using? You might want to add some peroxide to the water to kill off any unwanted organics.

Most people go to either 50% cloudy or till you start seeing ambers. Your choice. 50% cloudy is more psychedelic and amber is more couch lock. I prefer about 5% amber personally.

As for your red circle, that is what is called a pre-calyx and is normal for some plants to develop it at internodes.

are the pre-calyx the start of more buds ?
Should I keep using low nutes till they form ?
Thanks

The pre-calyx is just a single calyx that forms where the internodes on the stems are. They won't form into buds and not all plants have them. That pre-calyx is how people sex seeds in veg as it tends to form then. Just continue your normal regimine.

It is probably a mechanism to ensure seed production if a male polinates too early and buds haven't formed yet. Just a guess as to it's purpose.