Looks like nitrogen toxicity, the clawing the dark dark green leaves are classic nitrogen toxicity signs. If you havent fed yet, then I'd guess there are nutrients already in the soil. From a quick look on their website they say "This gives Light·Mix® a medium Electrical Conductivity (EC) value".
A "medium ec value" is a pretty shitty Guage but they are trying to tell you its already got nutes in it.
I'd flush the soil the real good with Phd water. What's your watering schedule like? Are you letting the soil dry out pretty good before watering again?
It says "light-mix" but I can't find ingredients anywhere which is highly suspect imo. A properly made organic soil should not be causing burn, especially when OP isn't even using nutes yet. Their info on their website says "Larger quantities of fertilizers may be applied on demand to any kind of plant, including heavy feeders, without the risk of overloading the substrate and causing nutrient burn." which I find quite odd. It is saying you can use larger quantities without causing burn, yet the medium alone is causing burn.
I'm no expert, but if I had to take a guess I would imagine they either didn't properly compost the compost that went into the medium. That, or they used something hot like guano or blood meal in the mix. However, without a list of ingredients it's hard to say for sure. This is exactly why I make my own soil from scratch, you're putting an awful lot of faith in a company by using their soil as opposed to doing it yourself. For a "light" mix, there is absolutely no excuse as to why your girls should be showing signs of burn right now. I'm at a complete loss as to why you're experiencing toxicity of any sort. Either the mix isn't as "light" as they think it is, or the compost wasn't finished properly before being added to the medium.
I have no experience with auto flowers so forgive me on that, but you say you're expecting it to go into flower soon yes? If at all possible, I'd recommend transplanting them into a more reliable medium as soon as possible. If the medium you're using is already causing problems this early then I can't imagine how it will go as time goes on. Certainly not something I would want to take a risk on come flower. I know re-doing the medium is not ideal, but it certainly beats the hell out of losing yield/quality because of poor medium. However, I have zero experience with auto-flowers so I'm not sure if re-potting will hurt more than it will help. Might hurt more than help at this point since you say flower is coming soon.
Personally, if it were me I'd just leave it be for a few days and see what happens considering the circumstances. If you flush the soil then your girls won't have access to those nutrients when they actually need them, if you do go through with flushing you'll need to make sure to top dress to compensate for all the nutrients you're losing. Normally, when the microbes go about processing the organic material the nutrients they exude bond to the soil so they can't get flushed out with watering. But that is only if your microbes are doing their job and the soil they are in is balanced. The fact that you are experiencing toxicity of any sort in an organic soil leads me to believe that Bio-Bizz messed up somewhere along the line and there is no balance in your soil and probably never was. So this leads me to believe that there is a lot of organic matter left in your soil that still hasn't been processed by the microbes just yet.
I'm not trying to sound like an elitist or anything and please don't take my reply that way. It's just that this is something that can easily be avoided by preparing your own mix. Once that Bio-Bizz soil starts to get more balanced you'll start seeing better results. I'm thinking they either didn't let their compost finish decomposing before adding it or they added way more bat guano to the mix than they should have.
Best of luck to you!
