I don't think you can blame the thickly spread slug pellets for yellowing leaves. I'd blame lack of water, or even possibly, overwatering. You can always pick up some of the excess of slug pellets and spread them somewhere else.

It's better IMHO to use the newer "organic" type of slug pellets that are based on ferric phosphate. These don't last as long as the older metaldehyde based ones, but they're a whole lot less dangerous to children, pets and wildlife and supply a small amount of phosphate (which is a constituent of plant food) as they break down.

Thanks. I also did not think the pellets are at fault but just didn't want a helpful friend to get in trouble by spreading too thickly.
Over watering is a possibility although this garden is in California and only gets drenched once a week. If that is over watering a once a week shower.... Not sure.

Let's say not over or under watering. Yellow leaves means.......

I don't know what temperatures you have, but I would think that underwatering is quite a possibility.

Yellow leaves can mean too little water too often. If the slug pellets have a clay base, that is often mixed with lime as a binder, and the lime will make the soil more alkaline, possibly causing an iron deficiency.

Hi just read this and think this is lack of water but can possibly be the slug pellets, i think next time the best solution for getting rid of slugs and snails in your garden is the SLUGBELL. See www.slugbell.com, its " The Worlds Best and safest slug control device". It protects Children, Cats, Dogs, Garden Wildlife, and our environment. Try it!!