@GreenCaciqueHawaii before answering the question should consider or think about something first about ec/ppm and how and what were measuring and how it can be different for different medias and nutrients.
What were measuring is the electrical conductivity of the water. so typically as we add more nutrients were adding more materials that make the water more conductive thus increasing our conductivity and our ec/ppm reading.
But some materials are better at conducting than others, such as the components that make up fertilizers, some may contribute a crap ton of nutrients but add very little conductivity, where as others may add 2-3-5 times the conductivity in say the same amount of nutrients usable by the plant, just cause they are made up different. Some medias such as soil also decomposes which breaks down the soil to release nutrients styore in the soil so long as you have healthy bacteria going, where as inert medias contribute nothing so you have to supplement completely with fertilizers so a plant can grow
So saying that EC's are only comparable with same nutrients, and same media's.
But how much can you push or have i ? well as much as the plant can take, but there is a balancing point or happy range per say where the plants are comfortable, go out side that plus or negative then they don't like it, but other factors come into it such as watering frequency, alternating feeding periods with straight water in between, to forcing runoff or having none.
saying that 3k is quite high, can be done if followed by plain or lower feed waterings but not forever and really that depends on the nutrient, say if it was miracle grow your plant would be dead.
The stretching though probably heat induced or hunting for light or a combination of things.
Always look at a plant as a whole, like your plants look super healthy up top but say your lower leaves down low may not be getting as much light or because your plant is starting to flower hard and you dont have much lower foliage going on its pulling hard on the couple leaves you do have as they redirect energy up top.