the yellowing is most likely the soil you are using, MG soil just isnt that great for herb plants plus it usually has some sort of ferts in it which isnt needed for the first 3 weeks or so.

what i would do is find some organic soil at a flower shop, should cost no more than 5-6 bucks a bag, and transplant them into the new soil, if your careful and dont mind taking the small risk i would break off all the old dirt from the roots before i placed them into new pots that way you know the old ferts are no longer present.

when my cab was running in the 90's my plants didnt look that great until i was able to vent the area better which is what it sounds like in your situation, they do grow in high heat they just take a lot longer than normal and give off a shitty appearance.

was you able to obtain any tools yet?

get more pics up too.