Pin holes in plants

I've got an established 58 gallon tanks, fertilizing with EI, running pressurized CO2 monitoried with a 4 dKh drop checker--all stuff I've learned about here. But I have a question/problem. The crypts and swords in my tank all have small holes in the older leaves. The tank is established, so these aren't from a transition (like recent planting). I prune the leaves when they get too "lacey." Soon enough, the newer growth develops the same holes.

I haven't noticed any obvious signs of deficiencies--no yellow or curled leaves--just the holes. I've been trying to convince myself they are the work of the SAEs or the clown pleco (one of the latter, four of the former). I feed the pleco veggie wafers and would happily take him/her back to the LFS if I could only catch it.

So... here's the question: are the holes the work of fish or should I be looking for something in my water chemistry?

I can post pictures if necessary.

Thanks.

 

Lighting etc

I have 3 wpg. That hasn't changed, nor has tank pruning. The holes are a long-standing problem (months), not something new or occasional.