So sorry for your plants! Fertilizer "burn" is when the plant takes in plant food too quickly most often when liquid plant food is used on a hot day on dry soil or by using too much fertilizer. (Always read and follow directions on label - but hey, we all goof up sometimes.) The solution is water, water, water. By flushing the soil with lots of water as soon as you notice the problem you will be washing out the excess nitrates that are causing the problem and hopefully the plants will adjust and survive. Water heavy for 2 or 3 days.   Hot weather contributes to fertilizer problems so I like to fertilize on cool or cloudy days. To keep things simple I also recommend a slow release plant food like Osmocote applied around the plants in the spring. You won't have to worry about fertilizer burn even if you accidently apply double the amount. This is because the semi-permeable membrane around the fertilizer releases the nutrients gradually as they need it. You might also want to apply a mulch of wood chips around the base of the plants after you flush the soil with water. The excess nitrogen in the soil will go to work breaking down the wood chips to the relief of your over fed plants.   Keep growing, Marianne Binetti