So there were no drain holes to begin with, right? Hmmm, bad news. Or were they just plugged? Good well draining potting soil? With 2 plants I sure hope it is a "huge" container. ;)

Hopefully you caught it in time to reverse the root rot that had developed and the plants will recover. The yellow leaves will likely die and fall off but new growth should follow. Tomato plants are tough! ;)

I'd suggest going really easy on the watering for some time until the soil has a chance to dry out well. Good luck.

Dave