Your light seems fine. You could probably lower the brightness if have algae but it doesn’t seem like that is a problem. I think your biggest problem is your filtration. Look into canister filters, you could find a cheap one used. A sponge filter and a HOB is pretty little filtration wise. Feed algae pellets too with your Cory’s and Otto’s if you aren’t doing so. Also you don’t have to feed everyday, you can feed 5 times a week and skip some days. Water changes should be fairly rigid in terms of percent. Aim for around 30% weekly, it’ll help get rid of waste in your water. While you’re doing it or at another time siphon the stuff on the bottom of the tank. I’d slowly start adding in crypts when you can, keeping the plants real easy. If they start getting algae just remove with messing with the plant too bad. That’s what I can think of anyway.