French snow pea help

Hello, so I planted some french snow peas in a sheet mulched raised bed about 3 weeks ago. I noticed a week after super heavy rain the top leafs are yellowing. Could it be a disease or just overwatering?
I am new to this so any help would be amazing
Thanks

Hello Andrew, could you tell us a little more about the soil conditions? What have you used to build the bed and mulch? Is it a new garden bed or have you planted in it before? Any other plants showing this condition? Full sun or shade etc. What have the low temps been like ?

So the location gets probably around 8-10 hours of sun.
The high to low is around 40-70 ferinhite, and a week ago it got to 30 with very heavy rain for 2 days.
This is colorado and it's usually pretty dry, but we have been getting a lot of rain.
It's in a raised bed about 12" high, lasagna style.
The layers are:
Aged cow manure- 2-4 years old.
Hay,
Sprinkling of work castings,
Aged Manure,
Hay,
Then 2-4" some planters mix consisting of manure, compost and topsoil that I bought from a soil yard.
They where planted in a 1" deep row with legume Enoculant.
The shelling peas up the row are more green with only a couple a tops slighty turning yellow.
The favs beans in the front of the picture are very green and happy. The onions next to the peas are happy as well.
My guess is that it was over watered?
Or could they be hitting pockets of nutrients and will just outgrow it?
Oh and the beds where built in March this year.

Ps. On top of all the info I gave, do you think a sheet mulched bed that's not layered like a lasagna will perform as well as a layered bed?