The issue I’m having is that during lights off, humidity shoots upto 70% and with lights on it roughly sits around 50% hence why I leave a dehumidifier on during lights off. I only have 4 plants in a small 1.2m x 1.2m x 2m tent, I have an intake fan and an extractor fan as well as 2 oscillating fans so perfect air circulation in the tent but not sure why humidity shoots upto 70% ?
Humidity is strongly dependent on temperature. Anytime you have air that is getting colder (like it does at night) it will increase in humidity. It's because hot air can hold more water than cold air. So when the light is on the heat from that is what is reducing humidity.
You could try switching on the lights at night instead of the day, as that could help. Ideally weed wants temps to be cooler in the dark periods.
Also....I don't really see any foxtailing in there...as someone else mentioned. And even if it is starting to foxtail, it doesn't sound like you'd be able to do much to stop it.