I've had the terra cotta experience. Once. :jointsmile:

Using the other pot to lift the plant out of the runoff is fine, and is a good idea. Just trying to cover all the bases. :thumbsup:

Plants, like people, have a rough day now and again... Nothing looks overly traumatic, and likely is something as simple as rootbound and/or transplant shock. Old leaves are old news, but keep an eye on the new growth.

Are you using the Grow Big as a stand alone...no Big Bloom? If so, doubtful that 2/3 dilution strength would do any harm. I've been using the FF line for years with good results. Not sure if you've heard, but when using Fox Farms, salt build-up might show it's head. I do monthly flushes, (1st of every month) to prevent this. (1 gallon of properly ph'd water to one gallon of pot size)

You can also split the weekly dose in half, but feed twice a week. You end up with the same weekly quantity of nutrients overall, but are 'softening' the effects of a full strength application. I've been doing this for a few years now. Older seedlings (3rd or 4th true leafsets) and rooted clones seem to prefer this approach.

Ya might have better results by letting them have a couple of weeks of the growth nutrient schedue before the switch. Push the process too quick and they tend to stunt the growth, affecting yield. You'll want to make sure they are good and healthy when they switch to flowering. (are you going to be using Tiger bloom in flower?)