I don't think 300w is too much light........I run a 650w in a 4x4 tent with excellent results.
Rule of thumb.......approx. 30 actual watts of led per s/f of grow area.
Agreed.......feed several times a day to substantial run off.
A plant that size in coco cannot be over watered. Coco holds 30% oxygen when completely saturated. Feeding to run off restores the nutes, pulls in fresh oxygen to the roots, and prevents salt build up.
According to GH........add silica first, then calmag, then micro, then grow then bloom. Mixing in the wrong order or mixing the 3 part in it's concentrated form will result in nutrient lock out.
Are you saying you were mixing the micro, grow, and bloom together before you added them to the water?
If so, big mistake........read GH's mixing recommendations.
I use tap water and never have to add a calmag supplement.........but that's me.
Why don't you just hand feed all three plants? It's obvious the autopot plants aren't doing as well.
Coco works best in a drain to waste method.
I don't think either plants in the autopots look good.......just my opinion.
There's a reason the hand watering plant looks better.
When you say the EC is 1700......do you mean the ppm's are 1700 or the EC is actually 1.7?
Are you hand feeding the one in the front? Because it looks fine.
1700 run off is extreme........probably caused by not having any run off.......salt build up big time.
Consider hand feeding to substantial run off at least once a day and never use plain water........if you have to flush use a...