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You mention that you are growing your plants in a covered porch. Hardening off the seedlings involves moving them slowing to the outdoor environment.
They need time to adjust to the sunlight, wind and temperatures.
Move them to a sheltered area a few hours a day and get them used to the change.
Here is an article that explains this important step in the growing process.

https://www.gardeningknowhow.com/garden-how-to/propagation/seeds/how-to-harden-off-your-seedlings.htm

These little bumps are actually roots.

https://www.gardeningknowhow.com/edible/vegetables/tomato/white-growths-on-tomato-plants.htm

The pale leaves could be a sign that they are getting too little light, too bright light (sunburn), or too much water. Check the moisture levels in the pots and make sure the surface gets dry between waterings.

The planting medium should be moist. Never soggy or dry.

https://www.gardeningknowhow.com/edible/vegetables/tomato/growing-tomatoes-from-seed.htm

You live in zone 6a. The average last frost date is between April 21-30.
These dates are guidelines and weather patterns can change how and when seeds and plants should be placed outdoors.

Heavy rain can certainly dislodge, wash away or cause seeds to die off.
The same can be said for small seedlings and even much larger established plants. Mother Nature can be harsh and this is a frustration to new and seasoned gardeners.

There are a few things you can do to try to protect your investment in the garden.
These links will help you.

https://www.gardeningknowhow.com/edible/vegetables/onion/onion-frost-cold-protection.htm
https://www.gardeningknowhow.com/plant-problems/environmental/protect-plants-in-freeze.htm
https://www.gardeningknowhow.com/garden-how-to/tools/using-cloches-in-gardens.htm
https://www.gardeningknowhow.com/edible/vegetables/vgen/row-covers-for-garden-plants.htm

Try not to become to frustrated if you lose some of your plants. It's very early in the season and you have plenty of time to get your garden going.
The soil needs to be at least 55 to 60 degrees for most seeds and plants to grow and do well, with the exception of cool weather crops like Peas.

A garden started later can and usually does better then a garden started in cold soil temperatures.

That would probably lead to stem rot and a fungal disease known as dampening off. The best course of action is to increase the light source and water less. Seedlings become leggy from lack of light and too much moisture . This article may help
https://www.gardeningknowhow.com/garden-how-to/propagation/seeds/leggy-seedling.htm