Can't determine much from a dead piece of wood. Please post an image of the affected plant.

a trace amount of flouride is normally added to tap water for human use. yellowing of new growth and burn of the leaf edges are the effects of it on susceptible plants. it can not be easily aerated not much like chlorine due to its chemistry. it may also be found as unsuspecting hitchhiker on fertilizers containing super-phosphate and other soil additives. there are multitude of ways to minimize and possibly get rid of flouride, but first, identification of the problem is critical, as application of products may damage your plant further rather than you expected. flushing the plants is a good start to minimize particulate matter accumulated.

Not sure from what though. Manure isn't high enough in nitrogen to produce a burn I would think

Can anyone tell me what is wrong with my Portulaca? Leggy, limp, pale plants. Thanks