PH is 4.9- BAD batch of happy frog.

Dolomite lime will buffer the pH and bring it back up into a usable range(and add some cal/mag). It’s sold as Garden Lime in most garden centers for about $5. Make sure it’s dolomite lime and not hydrated lime. First thing you should do is amend your bags of soil with it since it needs time to break down. Add 2 tablespoons of lime per gallon of soil or about 1 cup per cubic foot. I’m not sure about adding any to the solo cups but I’d just transplant them to bigger pots after you lime the soil. I see you have Recharge also. I’d wet the soil with some of it after amending so the microbes can start breaking down the lime quicker.