I use Jacks Classic 'Dynamic Duo' and supplemental cal/mag and bloodmeal for my nutes. FFOF soil has enough nutes for 2-3 weeks of veg, then they really need some N.
My first thought was heat stress, but he says his light is 20 something inches away and under 80F in the grow area. Almost impossible to have heat stress with those temps.
The regular pro soil has added nutes, so it's possible it could burn your seedlings. I would get some pro plus soil as that has no added nutes and mix it 50/50 with the regular pro.
I really like Fox Farms' Ocean Forest soil; yeah it's expensive but you get what you pay for. As for a quality strain, Cali Connection has some great genetics.
I prefer the taste of soil grown bud over hydro; tastes more earthy. "Hydro" bud being the best is just a hype. Only reason hydro is better is it grows a bit faster and you can control nutes easier; higher start-up cost though.