For the upcoming season I am wanting to graft all my tomatoes onto disease resistant rootstock. I chose RST-04-105-T from Harris Seeds and started 4 test seedlings. They are very slow growers, but around 3 weeks after germination they start showing signs of disease, beginning with white bumps on the stem, and then they start to hunch over, and the leaves curl upwards until they are rolled up. So far two of the four have had the same problems and I'm hesitant to start any more until I figure this out. None of my regular tomato seedlings have exhibited any type of behavior like this.

The soil for all my seedlings is moistened and then microwaved for 4 minutes, reaching temperatures up to 200 degrees to sterilize it in very small batches. The soil goes into a coconut coir shell molded for starting seedlings.

Does anybody have any idea what is going on? It's strange to have this happen to a plant that is supposed to have resistance to TMV, Corky Root, FW (1,2), V, Root-knot Nematode, Bacterial wilt and intermediate resistance to Southern Blight. I have another rootstock on order to try out in case this is something insurmountable.