It could be a potassium deficiency. The small holes on the Hygro do look like potassium deficiency. See Potassium Deficient Hygro. Corymbosa:
http://deficiencyfinder.com/?page_id=598
You'll want to add something with potassium in it to raise the level up to about 15-30 ppm potassium. You can add it 3x a week in 10 ppm doses. I like to use K2SO4 for this purpose. Use calc.petalphile.com to calculate how much K2SO4 to dose for your tank.
The old leaves will not heal, but no more leaves will develop holes if it is potassium. You should know in a week or two if the issue was potassium after you add it.
Also, excel is usually used to spot treat algae using a syringe to apply the excel directly to the algae underwater. Adding it to the water doesn't really stop algae that much. Also, excel doesn't kill every species of algae. It has almost no affect on spot algae. It is usually used to kill black beard algae.