Hi, Well the key isn't when to fertilize, but what to use. What is your husband using? It sounds like it's way too strong for your plants. I suggest the best way to grow veggies is to start with rich, organic soil. In the spring, mix in compost, rotted manure or any organic matter you can find. I use rotted horse manure and my plants do great. Now, if you want to still fertilize I suggest you use a slow-release granular fertilizer which releases the nutrients over the course of the summer as the plants need them. A brand such as Osmocote is an example. Slow-release granular fertilizers basically take the guesswork out of feeding your plants and minimizes the risk of burning. Apply the fertilizer in the spring according to label directions. You can buy Osmocote or fertilizers like it at most garden centers or home stores.