Parlor Palm leaf damage

[Robert D. Young]

I have parlor palms at the office that were in good shape for 4+ years but suddenly are declining. I thought some of this could have been from sunlight damage, or insect damage, or perhaps a wrong soil formulation. Any ideas on what to do here to reverse the decline? 

[Robert D. Young]

Here are more chamaedoreas with unidentified damage. Any advice as to what caused this is appreciated, as this did not happen for the first 4 years...

[fotodimatti]

which species is the last photo?
The damage looks similar to that on my Chamaedorea seedlings.

[Robert D. Young]

2 hours ago, fotodimatti said:

which species is the last photo?
The damage looks similar to that on my Chamaedorea seedlings.

Most are chamaedorea elegans but the tall one is chamaedorea oblongata. 

[fotodimatti]

Thanks! As I just learned in this forum, my chamaedorea anemophila seedlings here may suffer from too wet soil. Do you let the soil dry out between waterings?