has anybody tried the plant food sticks from lidl?

Hi folks  being on a budget and still a newbie, I know nothing about feeding plants, mine have got by on strong will and determination until now!

I have some multi purpose plant food for beds but not sure when to start feeding things like my sprouting dahlia tubers or lupin seedlings.

As they were only a quid I invested in. Plant food sticks from lidl, slow release for 100 days apparently. Has anybody had any experience using these or types similar?

Any thoughts would be greatly welcomed