They have them for tomatoes, potatoes, corn, etc.Anyone used them and think they are worth it, as opposed to an all purpose type? This will be my 3rd summer gardening on reclaimed lawn. I've been adding a lot of organic material and it;s a good loam. This year I will using my own compost, rabbit and chicken manure, wood ash, and worm castings. Do I really need to add any thing else? Don't care to spend anymore money than necessary, but I really want to have a "prize-winning" crop this year. Less than 2000 sf, Zone 7, SWVA.