Do I have a nitrogen problem or is it the strain

What kind of light are you using? I can only assume it could have vegged longer under stronger lights. Veg time is really dependent on the light source, how you train your plants, and how you water them. Those little guys could have probably done better in a smaller pot with more frequent watering. They still look good though!

 

Air to the roots is important for rapid veg growth. What happens often in a larger pot is it can retain too much moisture for too long and basically water log the roots so they can't get air which the plant needs to complete growth reactions. The roots take in oxygen. The leaves take in CO2. The roots rely on the structure of the medium in the pot to make sure they get enough air.

If you don't build the medium with enough perlite or other water absorbing/compaction resisting/drainage promoting material it will cause slow growth even in a fabric pot.

That's the reason you use fabric pots is to get more air to the roots.

It doesn't look like your pot is elevated out of the drain tray. Start with that. If you pot sits in the drain water then you can't even rinse out excess nutrients. They get soaked right back up into the pot. It also exposes like 25% more surface area of the pot to the air further increasing aeration to the roots.

You definitely have a darker green color to the leaves which indicates excess nitrogen but you're not quite toxic yet and not really experiencing so much negative symptoms from it so you caught it just in time.

Fix your medium and transplant if need be or just elevate the pot. Do a flush of the medium with clean ph'd water to get rid of any buildup and let it sit for a few days to dry out. Then come back feeding about 50% as much N as you were before while at the same time increasing the P&K ratio compared to N in the feed. Basically only reduce the N portion and keep the P&K the same if your supplements allow. If not you'll just have to cut all feed in half until the plant seems like it needs more again.

I use about 20% course perlite with promix for my medium. I supplement with soil sulfur and a little extra dolomite lime. I use fabric pots and feed with mostly GH flora micro/bloom with the lucas ratio. My plants get fed either daily or every other day based on how large the pot is for the plant. Waiting 5 days between watering means something is wrong about your setup IMO. It shouldn't take that long to dry out. It's summer time here. My room temp is 82-84 at peak often. They're pretty darn dry by the end of a single day right now. Mine would be dead in 5 days.

 

Ocean forest is notoriously hot soil. Stick with ph'd water until you wash more of it out. You could do a flush to try to get some out.

Some cal/mag supps can be really high in nitro. Advanced nutrients has one that's 4% nitro. Almost don't need a nitrogen supp with a cal/mag that high.

 

The slow growth probably has a lot to do with that light. It's not that powerful of a light to begin with then you made it even less powerful dialing it back for 2 months. I used to grow in ff soil. It doesn't need flushed.