I'm new, first grow, so take this for what its worth, but I ran into nitrogen toxicity when my youngest plant was coming out of veg. I flushed and she got better. 950/1000 maybe a little low, and ph has to be right for balanced uptake. As a new grower my rule of thumb is to hold off on nutes if I know its toxicity. If I suspect deficiency, or assumed toxicity doesnt improve I flush to the right ph and refeed with 1/4 strength nutes. In either situation i wait a day or two and make sure the issue doesnt fix itself.