Second year in a row that the rootstock seedlings have contracted this stem disease. Is it Alterneria? Planted in Espoma organic premium potting mix. Perhaps overwatered.

It looks like edema. It is usually caused by too much water and not enough light. The plants usually recover nicely once place outdoors. Try backing off the water and bringing it closer to the lights.

MissS! Thanks, will give it an attempt! Heirlooms and Hybrids...sown in diatomaceous earth two weeks earlier than Maxifort... are looking strong

@Harry Cabluck Your other plants look great. Can you wash the soil off of your root stock and transplant them into the DE or a mix of DE and Espoma? I think that they would do better for you planted that way. They just seem to be too wet and DE dries out nicely.

@Harry Cabluck im having the same issue. My heirlooms are doing fine but my fortamino rootstock have edema and look awful. All grown in the same condition.

I thought rootstock was supposed to be more resilient, what gives?