Hi, this is my 1st post here and I am new to planted tank.
I started growing HC using dry start method 2months ago. I flooded my tank 2 weeks ago and everything seems fine until my 1st (20%) water change after 1st week of flood.

Today is approximately the 2nd week of flood. I noticed some patches n dark spots on the leaves of HC. Anybody can help to advise what's happening?


Pic #1



Pic #2

Tank size: 39cm x 22cm x 25cm
Light: 2x 14W T5 tubes
Photoperiod: 10hrs
Non-CO2
Daily Excel dosing
Alternate day supplement of CO2 tablet
Weekly supplement of liquid plant fertilizer.