Pea's rotting from the soil up

A plea for help from a very beginner gardener... I have a few pea seedlings planted in a planter in the conservatory. They have started what seems to be rotting from the bottom up. the leaves are very delicate and they have not grown much since planting. I have attached a few photos. Any thoughts, direction or advice, gladly welcome! Thanks in advance...

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Re: Pea's rotting from the soil up

Reply from Carol

Could it be powdery mildew? Maybe they are a bit too moist and it might be humid in your conservatory which moulds love.

Re: Re: Pea's rotting from the soil up

Reply from smtw

Not sure, there is no residue on the leaves. I was thinking that maybe they were lying too close to the soil since they are not climbing very well. So I have tied them up onto the poles. I'll cut back on the watering a bit as well to see if that helps. Thanks for your response!