aime...you have covered a lot of ground with your post! I have some questions...and possible answers. What makes you think the osmocote does not work with some veges? Can it be another issue? Secondly, the osmocote is slow-release, I think. What about the Vigoro you want to use?
I have been quite successful with my container veges and tomatoes. I have learned much. Many low-dose feedings are much better/effective than full strength feedings occasionally. Free-draining potting mixes are VERY important. Larger pots for spreading/aggressive plants like tomatoes are better. goodluck
