To save it you have to do nothing as what is happening is an over watering so you did too much and now you just have to wait for the medium to be dry again before you water your plant to settle a dry wet cycle with the soil . Be carefull the grow caps are retaining water ! BTW How did you get some grow caps ? i thought they did not released the product ! anyway the ecxess of water is creating a lockout , the plant can't absorb nutrients , maybe the roots are a bit damages , and they are starting to get yellow by the lack of everything but Nitrogen in particular as it's what they needs at this young age to get bigger
Wet/ dry cycle in the futur +let the medium get dry so do nothing