Plants are looking pretty good but there are some light spots in the leaves. That's not uncommon for seedlings but, when I look at your RH,
that caught my attention. At 26°C and 51%, your tent has the humidity level for late flower.
Below is a screenshot of a VPD chart. VPD is similar to "feels like" for humans - we do better in certain combinations of temperature + humidity than in extreme combinations.
The chart is in °F, my apologies, but it's not set up to deal with Celsius correctly.
At 26 and 51, your "feels like" is under the arrow on the right. That's a VPD of 1.4. In flower, cannabis will do best at a VPD of 1.2 to 1.4, the higher the number meaning that it's warmer and drier. At the moment, your VPD is about 1.4 which is on the high end for flower.
In the seedling stage, cannabis does best at a VPD of 0.8 which is really moist. Per the chart, at 79°F (26°C), your plants will do better at and RH of about 70%.
Why so moist?
A high "vapor pressure deficit" means that the amount of water in the plant is much higher than the amount of water in the air around the plant. When the air is warm and dry, there's not much moisture in it so the moisture in the plant will tend to be pushed out into the air. In nature, energy moves from high to low and that's what happens to the water in the plant. Water leaves the plant via "transpiration" and, when water leaves the plant, it's got to be replenished. That's how plants maintain temperature and that's how the majority of nutrient flow in to a plant.
When VPD is high, meaning that it's warm and dry outside the plant, transpiration increases which means water and nutrient uptake have to increase. But when seedlings are young, their underdeveloped root systems aren't able to take up water very well and that can lead to problems for the plant ("stress").
If you increase RH, the air around the plant will have more moisture, the plant won't have to transpire as much. That helps ensure that nutrient uptake stays in range.
Again, your plants look really nice but there are a few light spots, which is not unusual, but I'd try to get some moisture in the air so the plants don't have to work as hard.
The Pulse site is a really good source of info on VPD.
This page is a good primer.