[JustOneMore20]

If its brown algae, like soft brown and diatom like, it can be a result of low flow and sometimes low nitrates. That isn't always the case though and I've found it can just show up at times.

What is your nitrate reading? Are you still dosing phosphates? What is your usual phosphate reading?

Also, are all the plants looking healthy? If you have any dead or dying leaves, take them out when you see them.

I see the rust colored algae in your pics.....looks like diatom/brown algae. The other doesn't look dark green though does it (sometimes really dark colored BGA can look blackish)? That would lead to a totally different approach if it was BGA. If its hard to remove, then its not BGA. Its pretty slimey and easy to wipe off.

Honesty, I'd try to trim the affected leaves, up the potassium dosing for the holes in the leaves and keep dosing Excel. If you saw an increase in the algae with an increase in Excel, then dosing every other day is fine.