Do they have drain holes? If not, that's likely the problem.

Yes jean001; I have 5 drain holes of about 1/2 inch diameter in the totes.

Not very big holes - I have five 1/2" drain holes in the bottom of my 5 gallon buckets. ;) So that slow drainage plus the yellowing leaves means over-watering would be my best guess. Unfortunately over-watering is very common and causes more problems for plants than most everything else combined.

Your posts don't indicate your zone or location - you really need to add that to your sign-in - so I can't even guess what the weather and temps might be contributing to the problem but you can always use your hand, stuck deep down into the soil, to determine if watering is really needed. Never judge just by the soil surface.

Dave

I've had poor luck with MG Potting Mix in everything from SWCs, regular pots, as an amendment to a bark-pearlite mix, and even some wintersown perennials have done poorly.

I know that others have had good results with MG, but they make it at different places depending upon region, so that could account for the difference.

I have noticed that it tends to stay very wet for a long time, then dry out and get hard very rapidly.

It might help your containers to add a wick into a drain hole to improve drainage. You can use a strand of a rayon mop, or a piece of man-made chamois.

Also, MG potting mix has a very small amount of fertilizer mixed in. It's definitely possible that your plants have used it up and need more nutrients.

In any case, adding wicks and carefully fertilizing won't hurt. There are many others here than can provide better advice on fertilzing than I can.