Is it better to use the fertiliser bombs on immature or mature plants? I haven't used them before and want to start experimenting and get better plants to sell!

All of the fertilizers (the bomb included) must be used on immature plants.

I use the Fertilizer-bomb as soon as I have planted the seeds. I think, when you buy it, it's written: "The chemical works best on the newly planted seeds..."

Thanks folks! I appreciate you taking the time to reply.