Let them tell you what they want, if you look at them and see they are getting a little dry towards the end of the day add a 1/4 cup of water or so. Vice-versa
You want them in the same size pots... But since they are just starting, play it by how the little one reacts to 1/2 cup a day also. Might need more, might need less. It depends on too many factors to count, like air flow, RH, light intesity, etc..
The chemicals left over are not enough to take toll unless some serious over watering is done... Just keep these babies PH right and don't over nute them. Make sure to water without nutes every 3 waterings. This will stop salt build-ups.
I suggest 20/4 Until You see Growth is healthy again, But its really up to you... Things are getting too hot for your ladies so, trying dropping some hours and/or get adiquate ventilation..
DO NOT Use Distilled Water to Feed With! This Could Be The Whole Problem Altogether! But you need to get that Temperature Down, I suggest using a night schedule when it is cool outside.. Also keep humidity stable with constant air circulation, if its getting humid there is not enough...
People tend to think flushing is drowning the shit out of your plant... That is extremely false! Flushing is you trying to slowly and evenly remove excess nutrients from the soil that the plant is not going to be using anymore. Just because flushing rhymes with rushing, doesn't mean they go...
You are sadly mislead on your techniques/information. Maybe you should take a note or two as you read along! If you use a too high of nitrogen levels, you also increase the soil's mineral salts in which case takes water away from the plant while leaving the salts behind. As a result, the leaves...
Dont worry this Everything Is easily Fixable. You need to Water Without Nutes (Flush) Every 3 waterings. So 2 Times with Nutes, And Than a Good Little Flush To Even Your PH out and get rid of any Salts Built Up in the soil. I Suggest atleast give her A Half Cup PH Balanced Water WITHOUT Nutes...