can you show a picture of your mulch so we can see the size of it.

Cedar mulch and hard woods are a no no, they tie up too much nitrogen.
Compost is too water retentive ,keeping it too wet causes root rot. You can use compost but only as a minor part of the mix.

I am sure some gardeners can offer up their proven formulas for grow mix.
something Cheap and something that works well, may not be the same thing. Rememmber it all starts with the mix,investing a few extra $ will be worth it.