kianwei:

Maybe you could list some of the symptoms?

I'd also look at the soil moisture. Palms look dehydrated. Can't determine properly from photos, but seems like some palms have quite a lot of rolled-leaves symptoms. This could be due to boron deficiency, or it could just be due to soil compactness and water table issue. Found any "blind-tips" on the young leaves? Or "crinkled-leaves" that look like zig-zag shapes?

Can't see the older leaves properly, however does seem to have some chlorosis, so Magnesium deficiency could be present. I would be a little hessitant to say the same about zinc deficiency; no harm adding a little zinc now and then though. Would help palms grow better, and produce better bunches. Copper deficiency is also a question mark, so I would like to know if the palms were already characteristically limpy like in the picture, or was this a more recent development. Copper deficiency could also somewhat explain the rolled-leaves I see in some pictures.

Overall, I believe you're on the right track in your recommendation lar. Place looks very familiar. Which part of Hutan Melintang is this? Towards the river end?

Sg Tiang area ah? Ah... Then add one more: Salt water intrusion. The CEC of the soil is likely to be messed up, that's why so many symptoms associated with mineral deficiency. If you have the opportunity, go to NALFIN near hutan melintang-bagan datoh there, and look for Rajendran, the plant breeder/agronomist there. Talk to him about this issue. They had some problems with saltwater intrusion from the Bernam River, and large tracks of palm plantings had been affected. I believe they've somewhat rectified the problem now.

Sg Tiang area ah? Ah... Then add one more: Salt water intrusion. The CEC of the soil is likely to be messed up, that's why so many symptoms associated with mineral deficiency. If you have the opportunity, go to NALFIN near hutan melintang-bagan datoh there, and look for Rajendran, the plant breeder/agronomist there. Talk to him about this issue. They had some problems with saltwater intrusion from the Bernam River, and large tracks of palm plantings had been affected. I believe they've somewhat rectified the problem now.