[farmergiles]

Looks like you got the makings of a great grow op there.

RE the yellowing- better water or pH adjusted water can only help. As you say it may be that the soil is a bit hot.

Mostly I suspect the pot size, those bigger pots are massive for the size of the plants.
Because the roots of the plant cannot permeate all of the soil properly yet some soil is just sitting there in a fairly wet state. The plant cannot use that water until it gets it's roots in there.

It's a bit late to pot back into a smaller pot now I guess but in future try to pot up gradually so that the plant can get roots in all the soil available as you go along.

Be very careful not to overwater, because water is sitting getting stagnant it may lower the pH of the soil as it sours. Let the soil dry almost totally between waterings (obviously not so much that the plant wilts).

Once the plant manages to get bigger the problem should cease.

Edit- If you`re very keen to use big pots from the go, try thinning the soil with perlite or vermiculite