Pepper Plant Aborting Fruit

I'm looking for some advice with my first time growing peppers in a Letgrow 5L tank.
It's day 80, and up until now things were going well.
I did have 3 plants, reduced to 2 as one was struggling.
The best performing plant has two fruits growing well, but is aborting any new fruits, even those that are pollinating.

The 2nd plant is doing the same, and has never formed any fruit, but continues to flower.

EC is 2.2
Ph 6.0
Water temp: 19-20'C

Both plants suffered from edema, but improved after I added a dehumidifier, and got the humidity down to 60-65%.

My only conclusion is root space, and I'm considering removing another plant, leaving just the 1.
I would greatly appreciate advice, before I do this though.