First Time Hydro Grower - Plant Problems

Hey there, guys...

Love the site, and am excited to be making my first post, and hopefully get some help. I've entered the grow game... and built myself a slick 4x2x5 foot cabinet. I use a drip irrigation setup, which is recirculating, and waters 3 times a day right now, with Canna Aqua nutes. Before I make the leap into my marijuana grow, I decided I'd try a green pepper grow, just to make sure everything in my system was working. First off, I'm super excited... my plants are about a month and a half old, and doing great, but I do have a problem...

Some leaves have small holes, and some are yellowing on edges, whilst also curling and becoming almost "crispy". I have an EC meter coming to me via ebay in the coming week, and I'm not 100% sure, but I'm guessing nutrient burn, maybe? Just wondering if anybody had a different diagnosis for me. Here's some pics of the issue, as well as you can see some very healthy looking leaves as well. Any help would be GREATLY appreciated. Need any other info from me, just let me know.

Thanks guys!!!

Thanks, Xiphos. I try and keep things as clean as possible in and around my cabinet, and I have yet to actually see any bugs, but I agree in that it's strange to have holes appear like that. Seems funny for a nutrient burn to produce holes, but I'm new... The EC meter should definitely help me with that a bit, hopefully. I also only use 30 liters in my reservoir... so I understand it's probably a little bit less forgiving than a bigger reservoir. I'll keep an extra eye out for any bugs in there, thanks.