I think your problem was the introduction along with removal of co2. Plants get used to having a certain amount of co2 (they produce an enzyme called Rubisco to get co2, if co2 is in abundance, they don't need nearly as much of this enzyme and thus reduce their stores and use all their energy for growth instead of producing this enzyme..one of the reasons why co2 adds so much growth). If co2 is suddenly reduced, you have a bunch of very crippled plants. They no longer have enough of that enzyme to get carbon so not only can they not grow, they can't make more of the Rubisco. It's a long, slow process for the plants to get themselves back into condition to grow again. Sometimes the plants will start pulling carbon from other leaves on the plant, so you'll see leaves getting holes in them and dying off while others may appear ok. During this time, algae just starts running rampant, there is absolutely no competition. The process of converting back to non-co2 can take up to 6 weeks.

For a non-co2 tank, you need to stay with low light, and therefore you need to stay with low light plants. Any plants you have that are higher light will die off. Some of the lower light plants may die off too due to the unstable conditions. At the least, they will lose a lot of leaves.

In the meantime, you should keep things stable - get yourself a dosing schedule, fertilize 1x/week with EI as you normally would in a non-co2 tank, and I would go with about a 30% weekly water change. Personally, I would reduce the photoperiod to about 6 hours/day to limit the amount of algae outbreaks. Keep removing the algae as fast as you can. Perhaps reducing the lighting intensity could help too....I'm not sure but someone else might know if this will have an adverse effect on the plants or not. Get lots of algae eating fish. Keep ammonia at 0 at all times, it triggers algae to grow. Clean up dead leaves quickly to avoid decomposition in the tank, this can also feed algae problems. Keep dosing Excel.

I'm sure someone else will come along with some further insight for you but realize that you are looking at a couple of months before you really get things back in shape, so be patient and don't give up. Your tank is in transition phase now, you just need to keep it as healthy and stable as you can until it sorts itself out. As things improve and some plants die, you can start adding more healthy plants. Also realize that die off of leaves is pretty normal for most plants when they are planted in a new tank. They too are going through a transition and it takes time for them to get adjusted and start growing.