The thing about using organic matter like spent coffee or tea grinds to feed your plants is that in order for it to become available it must be decomposed by soil microbes so your plants can absorb it.
If you are using your soil as a sterile medium and primarily using nutrients to feed them top dressing w/ organic matter is kind of pointless. If you are growing in an active living organic soil then this makes more sense but keep in mind it takes a long time for whatever you add to break down. The more microbially active your mix is the faster the decomposition process happens. As it has already been suggested it might be better to toss your tea bags or coffee or whatever in a compost pile or worm bin first which will break it down much faster.