Posted: 18/02/2017 at 17:32
Do you mean there's 10 in one pot Hazel?
If so, it's not ideal, unless it's a great big pot, in which you can let them grow away for the rest of the season. If they're that small, I'd try and separate into bundles of two or three, into a 3 or 4 inch pot, let them carry on growing untill they're big enough to fend for themselves well , and be planted out in the big bad world in their final position, be that pot or border.
I assume you have them outside, and just protected from the worst of the weather? If not, and they're in a greenhouse or cold frame, you'll need to watch they get enough light or they'll get leggy. Pinch them out as they grow, so that they become bushy plants. Make sure they're not cossetted either - sweet peas are hardy
Ordinary compost is fine for now.