Rotala Macrandra 'mini Type 4' And Rotala Orange Juice Leave Discoloration

My rotala macrandra 'mini type 4' and rotala orange juice leave have severe discoloration, not in a good shape. I have no idea what went wrong, here are my spec and dosing regime.

Can advise me know what went wrong?

Mine is a 47gallon tank, 90x45x45cm.I using a zetlight zt6400 and chiller.
light is on 7hrs daily, co2 is on before 2hrs the light turn on and all the way till the light is off.
I try to achieve an 1.2ph drop.
Before co2 come on, tank ph is 6.7. After 2hrs of co2 on, ph is 5.5

I dose weekly
20ppm k
7ppm no3
7ppm Po4
5ppm Mg
0.4ppm Fe/traces

 

Here is my full tank pic. Left side lily pipe outlet is linked from my chiller and as for my right side, co2 is linked to the rainbar.

There is a small powerhead next to the rain bar and a surface skimmer right at the left hand corner.

 

One more thing to add, the surface skimmer come with a powerhead, which is blowing the water to the front of the tank.