my recommendation would be to get a good base nutrient, flush the medium with RO until you get the ppm as close to zero, then starting fresh with a 1.0 ec base nutrient ph to between 5.8...preferably on the lower end
Happy frog is literally peat and perlite...with nothing else...if it does it is so trace that it pretty much is non existent ........I also wouldn't be able to use FF nutrients, even if free......for around $25.00 you can get GH Micro/Bloom or a gallon of CNS17 etc....and that would work great.....or a dry nute....hell Maxibloom works great from beginning to end
you can use Maxibloom @ 5g per gal which gets you around 1.4ec... and do a feed/feed/tea.....for the tea just use the Big Bloom...which is a concentrated tea which works great......
this would be my recommendation