welcome to GoY

when you say geraniums do you mean the bedding ones also called pelargoniums or the perennial ones.

could you add a photo.

as for replacing them go to your local gc and there will be plenty of alternatives available.
but I wonder why these plants aren't happy. are they getting enough water and do you feed them regularly.

you could try to save the ones you have by cutting off any dead leaves and flowers and give them a good watering and feeding. where are the pots stood?

If you mean pelargonium geraniums, a photo is probably essential - they are generally healthy plants, not prone to infestation or infection UNLESS you've had nothing but wet weather and they're fully exposed to the elements,so I'm wondering why they look ghastly...

You can add a photo to your question - you should see an "add a photo" option.

They are pot bound. It's time to divide and conquer. Get them out of their pots cut the plant and root ball in half and replant. Do it now while there still is time.