growing in just potting soil..good idea?

Hey everyone I am growing two plants in a little grow box I made and right now they are in pots with pure potting soil. It seems like they are growing a little slow. Is it possible they are growing slow because it is just straight soil without any perlite or similar substance mixed in? The soil does seem pretty dense. So would it be a better idea to mix with perlite?

You got it spot on!
dense soil causes poor root development resulting in slow growth...
mix up a better batch of soil and transplant to bigger pots.

You should get a 3cubic bale of sunshine mix ,or pro mix it's realy light [soiless] soil thiere is 0 nutrients in it it's bake in ovens to make sure it is fertile ,so you have to feed your plants a power soulubale [npk]It's almost like growing hydroponicly,but very easy.Your root system gets lot's of 02. i let them go dry,to the point of them willting,then i feed then 20-20-20- in veg and 0-50-30-flower,and thiere's no diffrents in waitting time.compared to hyrdoponic .all you need is a light source[400hps] 8'' plaslic [colored pots] no clear ,is bad .increase the dose of food has you go.i pull out 4to 5 oz's every 50 days .so it works good .

i add 3 parts soil, 2 parts perlite, 1 part vermiculite. tranplant into a bigger pot with a ratio somewhere in that area and water with some superthrive when you transplant. should recover quickly