In my opinion 50% phosphate is extremely high, nonetheless it will get the job done if it is all you got.
Judging on the pics you got atleast another month to go, but you need to get a magnifying glass to check out the trichromes.
As far as your growth problem: the only thing i can think of why your plants stretched, and the lack of secondary side growth is not enough sunlight. HOW much do they get a day?