Multi purpose potting compost will be fine, they don't need acid soil. You mention yellowing leaves on your other post - difficult to answer because of lack of other information. Where are they growing now? How long have you had them? Have they flowered already or not? Is it just the lower leaves?

For my lilies, grown in pots, I use a multi-purpose compost and it says on the bag 'with added John Innes'. They seem to thrive in that. However, as with all bought compost in bags I like to add extra drainage so always mix in some grit. I find the compost to dense otherwise. I also find lilies voracious feeders.....so feed well in the growing and flowering season. Good luck.