A 70/30 coco/perlite mix cannot be overwatered.........except for a small seedling in a large pot.
You should have started in smaller pots.......maintaining the proper moisture level will be a challenge. That's the cause of your slow growth.
Coco should be fed daily at a pH around 6.0 to...
The best way to know if your hygrometers are calibrated properly is to do the salt test.
Put your hygrometers in a freezer bag along with a water bottle cap filled with wet salt........the wet salt is exactly 75% humidity. Leave it for 24 hours and you'll know how to adjust.......if your meter...
There are many options.
You can use H3ad's formula........which is a version of the Lucas Formula designed specifically for coco. 6ml Micro, 9ml Bloom per gal. is full strength......you can adjust it accordingly using the same ratio.
Or you can use this which is proven and works well.
Good...
I would remove the growth beneath the ones you want to cut off and bury most of the stem when you transplant.
That growth is garbage and will eventually need to be removed anyway in most cases......and don't cut the leaves you wanted to cut.
Just my opinion.