chlorosis - Chlorosis may be a symptom of a number of different plant ailments, including mineral deficiencies (commonly, iron) and some diseases. It occurs as a result of reduced chlorophyll production, turning newer (usually) growth yellow. In established leaves, areas between the veins yellow first. Definition from: http://www.earthandtable.com/

More information about your growing situation might be helpful. What is your system type & solution pH? What is the composition of the "Hocklecm" solution? Did the symptoms start on the younger or older leaves first, & are the stems, roots, plant growth, etc., affected? Does the chlorosis affect the entire leaf, margins, veins, etc.? As Hank above said iron is a common cause. What kind of iron is in your nutrient mix?

thanks for the reply.

My solution consist of Ca(No3)2.4H20 (1,17ml), KNO3 (0.5ml), MgSO4.7H2O (0.5ml), KH2PO4 (0.14ml), EDTA (0.26) and organic solution consist of (MnCl2.4H2O), H3BO3,ZnSo4.7H20, CuSO4.5H2O), H2MoO4.H20 dissolve in 1 liter( 1.0ml)). And then make up to one liter with distilled water.

The chlorosis affect only the leaf (make it looks curly and dry), young leaf healthy (take about 3 weeks to produce new leaf = take to much time) at the moment. New roots grow after a week and the stem are okay now.

Right now, I have another problem. Two of my tank (50cmx30cm), the span/foam that support the plant colonize by algae and one of the that pH drop below 5.0 (all my tanks pH is above 6.0). I change the solution every 2 weeks and i didnt use any aeration. Should I use aeration?

One problem with algae is that it affects pH because of its photosynthesis. Also, when it dies it decreases dissolved oxygen. Aeration is usually advised since it can help keep down algae. Making sure your system tank & tubes are not exposed to light can also help.

Your chelated iron is a good soluble iron, but remember the higher the pH the less the iron is absorbed.

Here are some leaf symptoms:

Leaf curl
-----Starts on younger leaves; curled down: S
-----Starts on older leaves first
Upward or cupping: Mg, Mo
Leaves in general
-----Curled: B, P, K
Dry leaves:
-----B, P (dry tips), S
Chlorosis
-----Starts on younger leaves: Ca, Fe, Mg, K, S
-----Starts on older leaves: B, Cl, Mn, K, Zn

I read about your suggestion on how to avoid algae from blooming. The algae is growing around the plant pot and not in the tanks. And my experiment shows that, tank that put directly under the sun grows healthier (algae grows too) than the tank put under some shades (but attack but insect-mortality rates is higher). Another problem is, according to some expert regarding "centella asiatica", they said that it's optimum pH is around 5.5 to 8. But, somehow my plant can torelate till below 5 (and their leaf is much greener than those plant using soil as medium).