Hi greenpinky,
Any plant food has to get to the plants root system to start to feed it,
If you've a form of barrier between the plant and the way to this system its going to slow it down and if it's a boiling hot day 'even if you applied the granular feed the evening pre the hot day the feed may well be effected by the sun, "Try to feed late in the day when its cooler and the evening moist night air will help, and the moisture wont evaporate as it will during hot day tempature
I use liquid most of the time "but " If im using granular i lightly fork it in, (just scratch the top few inches) and then water,
Some granular feeds disolve when you water them ie epsom salts very quickly and others end up looking like weet a bix crumbs and tend to stick in the mulch should you apply them on top of the mulch,
Now ref the look of plants once you've applied the goodness feeds have depends on what they looked like pre you feeding them,
I mean if your plants are turning yellow or they're drooping or in the case of fruit the fruits not growing well, it may not be a feed problem you've got it's more of a care from the start problem, ie the soil/compost or the pots to small, the plants are not water offten enough, the heats to much the plants in the wrong place ie direct sunshine,
Its well worth taking your time and learning about what the plant needs are, And more important what they dont need,
PS just a small tip, so many plants are killed due to over watering/over feeding and also covering the plants leaves with feed,
Always feed from the bottom (this way the plant will give the top area whats needed) if you cover leaves with feed you stand a chance of the plants leaves being burnt "unless its a plant that needs mist feeding" and again find out what your dealing with? And water from the top,
Never let plants stand in water for long periods as they will soon have root problems (root rot) and it the main plant system is damaged then the plant cant grow healthy,
I hope this little lot helps
