I have same potty mix it will be fine is long as it's not like sand your plants some how could be etiolated but I think its just regular growth

No lights needed i plant outside or your plants just are slow

Can you post some pics?

It sounds like your succulents aren't getting enough light. A North-facing window just doesn't provide enough sunlight. What zone are you in? I don't know much about growing under lights, but I'm sure that more seasoned members will be able to provide you with some helpful information in that regard.

As for growing mediums, succulents and cacti like well-draining soil, as I'm sure you know. Most C&S mixes that you buy in store are regular, peaty spoil with other stuff like sand and bark added. You can amend this by adding at least 50% perlite (can be purchased at your local Home Depot/Lowe's/gardening centre), or, alternatively, you can search 'Al's gritty mix' on this forum. There are a lot of success stories, and recommendations for alternative 'ingredients' if you can't find some of them locally.

Good luck!

More light, artificial if necessary, or give away your succulents and try tropical foliage plants instead. They'll be happy in lower light levels, and you'll likely be happier, too.

Adapting your plant selections to your conditions is wise. Expecting your plants to do the adapting is hard on the plants.