The problem you're encountering is your tank is not in balance. When light, and nutrients aren't in balance, the result is algae. Once you have algae, it will also be competing against plants. We have many videos and articles on balancing an aquarium. I'm not sure what the par of your light is, but that will remain a constant as it's on a timer. Then depending on the plants you have/growth you adjust the fertilizing.
To get back on track, I'd probably purchase something like a Siamese algae eater or flag fish to start working on the staghorn algae. It also looks like you have some diatom algae as well, however your mystery snail is probably working on this.
With just the crypts in the tank, it'll be hard to balance as they need to little light, and feed from the substrate. You may find benefit in turning down your light if possible, or raising it higher, until your plant load is more dense. This will be a learning experience over probably 6-8 weeks for you to dial in lighting and nutrients. Fight off the algae and get the plants growing instead of algae.