I have read that it is magnesium deficiency, and in another post here they say potassium deficiency, but this started happening recently when I started dosing ada fertilisers (Brighty K, Minerals, Nitrogen, & iron) and increasing co2.
there probably is a deficiency there, and both potassium and magnesium can cause holes.I see you have shrimp and snails? the leaf on the smaller anubias definitely looks munched on. they're probably taking advantage of any small holes and making them bigger. my shrimp and snails will eat my plants and rip them apart. they usually don't touch anubias, but the young leaves are softer, so they could go after those.