Hi Susie -- Sorry to hear about your watermelon and squash plants and pesky rabbits.   

Poor germination and shriveling up of your plants can be caused by several factors. Since you have had luck with these plants in the past this may not be the case but it's always important to use fresh, high-quality seeds and to ensure they are planted at the correct depth and spacing. Make sure not to overdo a slow-release fertilizer like Osmocote as too much can stress the plants. It might be worth checking the pH and nutrient levels in your soil too as these can affect germination and plant health. 

There are at least three reasons your seedlings may not have emerged as they have in the past. One is due to damping off whereby the seeds may rot in the soil due to a fungus or mold. Another is due to the seed corn maggot and finally cooler than expected temperatures. See info on each at https://apps.extension.umn.edu/garden/diagnose/plant/fruit/melons/seedlingemergence.html. It applies to both watermelon and squash.

Here are a couple of additional websites about watermelon you might find helpful:

https://www.uaex.uada.edu/publications/PDF/FSA-6012.pdf

https://extension.umn.edu/fruit/growing-melons-home-garden#soil-and-fertility--1139160

Regarding the rabbits kale and snap peas are one of several favorite foods. Fencing, when done properly, is the most effective way to protect plants. Rabbit fencing should be at least 1.5 to 2 feet tall during the growing season. The fencing material shouldn’t have gaps larger than an inch, making chicken wire and small-gauge hardware cloth ideal. If fencing isn’t a good option, there several rabbit repellants on the market. Repellents try to deter bunny browsing via tastes or odors that rabbits don’t like, such as blood, urine of their predators, rotten eggs, garlic or hot peppers. The best time to use rabbit repellents is at the very first sign of damage – or before any damage – if you have had problems in the past. Deer-off, Liquid Fence and Plantskydd are three common repellents. I have tried a couple with varying success!

Good Luck!