Plants in my outdoor hydro are not growing

I got a late start this season and didn’t get my sun-hardened clones into my hydro unit until the end of July. This year so far, my clones have only grown an inch or so in 3 1/2 weeks and just seem to be sitting there with roots barely growing, despite the fact they are getting close to 10 hours of direct sunlight in mid 80 degree weather and I’m using nutrients at the recommended levels for aggressive growth phase.
Two of my nutrients are left over from last season but that has never been an issue before and I got an end of July start last year as well but had no growth issues.
Should I buy fresh nutrients?
Could it be because of my late start and should I mayber move them indoors and give them 18 hours or more of light?
i have never experienced this problem before and I’m totally stumped.

Do you have any super thrive or anything for the roots like some slf 100 or clonex clone root nutrient (not the rooting gel this is a nutrient solution for seedlings and clones for roots)

Do you have any way you can supplement light so they are getting 14 to 16 hrs of light?